diff --git a/doc/userguide/rules/intro.rst b/doc/userguide/rules/intro.rst
index 943600c54d0..5e56cee4110 100644
--- a/doc/userguide/rules/intro.rst
+++ b/doc/userguide/rules/intro.rst
@@ -251,7 +251,7 @@ Now, let's say we have a rule with the following header::
 Only the traffic from the client to the server will be matched by this rule,
 as the direction specifies that we do not want to evaluate the response packet.
 
-Now,if we have a rule with the following header::
+Now, if we have a rule with the following header::
 
     alert tcp 1.2.3.4 any <> 5.6.7.8 80
 
diff --git a/src/detect-engine-mpm.c b/src/detect-engine-mpm.c
index 97d43fb8d79..2488021821d 100644
--- a/src/detect-engine-mpm.c
+++ b/src/detect-engine-mpm.c
@@ -1071,12 +1071,14 @@ static SigMatch *GetMpmForList(const Signature *s, SigMatch *list, SigMatch *mpm
 
 int g_skip_prefilter = 0;
 
+// tells if a buffer id is only used to client
 bool DetectBufferToClient(const DetectEngineCtx *de_ctx, int buf_id, AppProto alproto)
 {
     bool r = false;
     const DetectEngineAppInspectionEngine *app = de_ctx->app_inspect_engines;
     for (; app != NULL; app = app->next) {
-        if (app->sm_list == buf_id && (AppProtoEquals(alproto, app->alproto) || alproto == 0)) {
+        if (app->sm_list == buf_id &&
+                (AppProtoEquals(alproto, app->alproto) || alproto == ALPROTO_UNKNOWN)) {
             if (app->dir == 1) {
                 // do not return yet in case we have app engines on both sides
                 r = true;
@@ -1232,7 +1234,12 @@ void RetrieveFPForSig(const DetectEngineCtx *de_ctx, Signature *s)
             }
         } else {
             for (uint32_t x = 0; x < s->init_data->buffer_index; x++) {
+                if (s->init_data->buffers[x].only_tc) {
+                    // prefer to choose a fast_pattern to server by default
+                    continue;
+                }
                 const int list_id = s->init_data->buffers[x].id;
+
                 if (final_sm_list[i] == list_id) {
                     SCLogDebug("%u: list_id %d: %s", s->id, list_id,
                             DetectEngineBufferTypeGetNameById(de_ctx, list_id));
diff --git a/src/detect-engine-state.c b/src/detect-engine-state.c
index 9fa5f72308f..cbdcd2d0aab 100644
--- a/src/detect-engine-state.c
+++ b/src/detect-engine-state.c
@@ -89,9 +89,9 @@ static DeStateStore *DeStateStoreAlloc(void)
 }
 
 #ifdef DEBUG_VALIDATION
-static int DeStateSearchState(DetectEngineState *state, uint8_t dsi, SigIntId num)
+static int DeStateSearchState(DetectEngineState *state, uint8_t dir_state_index, SigIntId num)
 {
-    DetectEngineStateDirection *dir_state = &state->dir_state[dsi];
+    DetectEngineStateDirection *dir_state = &state->dir_state[dir_state_index];
     DeStateStore *tx_store = dir_state->head;
     SigIntId store_cnt;
     SigIntId state_cnt = 0;
@@ -120,15 +120,15 @@ static void DeStateSignatureAppend(DetectEngineState *state,
 {
     SCEnter();
 
-    uint8_t dsi = (direction & STREAM_TOSERVER) ? 0 : 1;
+    uint8_t dir_state_index = (direction & STREAM_TOSERVER) ? 0 : 1;
     if (s->flags & SIG_FLAG_BOTHDIR) {
-        dsi = DETECT_ENGINE_STATE_DIRECTION_BOTHDIR;
+        dir_state_index = DETECT_ENGINE_STATE_DIRECTION_BOTHDIR;
     }
 
-    DetectEngineStateDirection *dir_state = &state->dir_state[dsi];
+    DetectEngineStateDirection *dir_state = &state->dir_state[dir_state_index];
 
 #ifdef DEBUG_VALIDATION
-    BUG_ON(DeStateSearchState(state, dsi, s->num));
+    BUG_ON(DeStateSearchState(state, dir_state_index, s->num));
 #endif
     DeStateStore *store = dir_state->tail;
     if (store == NULL) {
diff --git a/src/detect-engine.c b/src/detect-engine.c
index 6721512dade..5944869f3a7 100644
--- a/src/detect-engine.c
+++ b/src/detect-engine.c
@@ -1360,6 +1360,8 @@ bool DetectBufferIsPresent(const Signature *s, const uint32_t buf_id)
     return false;
 }
 
+// Tells if a buffer (from its list id) is ambiguous about directions
+// meaning it can match on both to client and to server, like http.connection for example
 static bool DetectEngineBufferAmbiguousDir(
         DetectEngineCtx *de_ctx, const int list, AppProto alproto)
 {
diff --git a/src/detect-fast-pattern.c b/src/detect-fast-pattern.c
index c73ca682e37..17c1fddb30f 100644
--- a/src/detect-fast-pattern.c
+++ b/src/detect-fast-pattern.c
@@ -244,9 +244,8 @@ static int DetectFastPatternSetup(DetectEngineCtx *de_ctx, Signature *s, const c
                            "bidirectional rule with a streaming buffer to server %u",
                         s->id);
                 goto error;
-            } else {
-                s->init_data->init_flags |= SIG_FLAG_INIT_BIDIR_FAST_TOCLIENT;
             }
+            s->init_data->init_flags |= SIG_FLAG_INIT_BIDIR_FAST_TOCLIENT;
         }
     }
 
diff --git a/src/detect-file-data.c b/src/detect-file-data.c
index fc7e0601fd7..0f642f08673 100644
--- a/src/detect-file-data.c
+++ b/src/detect-file-data.c
@@ -152,6 +152,13 @@ static int DetectFiledataSetup (DetectEngineCtx *de_ctx, Signature *s, const cha
 
     s->init_data->init_flags |= SIG_FLAG_INIT_FILEDATA;
     if ((s->init_data->init_flags & SIG_FLAG_INIT_BIDIR_TOCLIENT) == 0) {
+        // we cannot use a bidirectional rule with a fast pattern to client and this
+        if (s->init_data->init_flags & SIG_FLAG_INIT_BIDIR_FAST_TOCLIENT) {
+            SCLogError("fast_pattern cannot be used on to_client keyword for "
+                       "bidirectional rule with a streaming buffer to server %u",
+                    s->id);
+            return -1;
+        }
         s->init_data->init_flags |= SIG_FLAG_INIT_BIDIR_STREAMING_TOSERVER;
     }
     SetupDetectEngineConfig(de_ctx);
diff --git a/src/detect-file-hash-common.c b/src/detect-file-hash-common.c
index e7bd692b9c7..1e7b142e798 100644
--- a/src/detect-file-hash-common.c
+++ b/src/detect-file-hash-common.c
@@ -333,6 +333,13 @@ int DetectFileHashSetup(
 
     s->file_flags |= FILE_SIG_NEED_FILE;
     if ((s->init_data->init_flags & SIG_FLAG_INIT_BIDIR_TOCLIENT) == 0) {
+        // we cannot use a bidirectional rule with a fast pattern to client and this
+        if (s->init_data->init_flags & SIG_FLAG_INIT_BIDIR_FAST_TOCLIENT) {
+            SCLogError("fast_pattern cannot be used on to_client keyword for "
+                       "bidirectional rule with a streaming buffer to server %u",
+                    s->id);
+            goto error;
+        }
         s->init_data->init_flags |= SIG_FLAG_INIT_BIDIR_STREAMING_TOSERVER;
     }
 
diff --git a/src/detect-filemagic.c b/src/detect-filemagic.c
index 2bd6b7ea12a..9a443a3bbd4 100644
--- a/src/detect-filemagic.c
+++ b/src/detect-filemagic.c
@@ -212,6 +212,13 @@ static int DetectFilemagicSetup (DetectEngineCtx *de_ctx, Signature *s, const ch
     s->init_data->list = DETECT_SM_LIST_NOTSET;
     s->file_flags |= (FILE_SIG_NEED_FILE | FILE_SIG_NEED_MAGIC);
     if ((s->init_data->init_flags & SIG_FLAG_INIT_BIDIR_TOCLIENT) == 0) {
+        // we cannot use a bidirectional rule with a fast pattern to client and this
+        if (s->init_data->init_flags & SIG_FLAG_INIT_BIDIR_FAST_TOCLIENT) {
+            SCLogError("fast_pattern cannot be used on to_client keyword for "
+                       "bidirectional rule with a streaming buffer to server %u",
+                    s->id);
+            SCReturnInt(-1);
+        }
         s->init_data->init_flags |= SIG_FLAG_INIT_BIDIR_STREAMING_TOSERVER;
     }
 
diff --git a/src/detect-filename.c b/src/detect-filename.c
index 66eb5777561..c42387dcdfe 100644
--- a/src/detect-filename.c
+++ b/src/detect-filename.c
@@ -179,6 +179,13 @@ static int DetectFilenameSetup (DetectEngineCtx *de_ctx, Signature *s, const cha
     s->init_data->list = DETECT_SM_LIST_NOTSET;
     s->file_flags |= (FILE_SIG_NEED_FILE | FILE_SIG_NEED_FILENAME);
     if ((s->init_data->init_flags & SIG_FLAG_INIT_BIDIR_TOCLIENT) == 0) {
+        // we cannot use a bidirectional rule with a fast pattern to client and this
+        if (s->init_data->init_flags & SIG_FLAG_INIT_BIDIR_FAST_TOCLIENT) {
+            SCLogError("fast_pattern cannot be used on to_client keyword for "
+                       "bidirectional rule with a streaming buffer to server %u",
+                    s->id);
+            SCReturnInt(-1);
+        }
         s->init_data->init_flags |= SIG_FLAG_INIT_BIDIR_STREAMING_TOSERVER;
     }
 
diff --git a/src/detect-filesize.c b/src/detect-filesize.c
index ec9279c838f..7814513a2f9 100644
--- a/src/detect-filesize.c
+++ b/src/detect-filesize.c
@@ -134,6 +134,14 @@ static int DetectFilesizeSetup (DetectEngineCtx *de_ctx, Signature *s, const cha
 
     s->file_flags |= (FILE_SIG_NEED_FILE|FILE_SIG_NEED_SIZE);
     if ((s->init_data->init_flags & SIG_FLAG_INIT_BIDIR_TOCLIENT) == 0) {
+        // we cannot use a bidirectional rule with a fast pattern to client and this
+        if (s->init_data->init_flags & SIG_FLAG_INIT_BIDIR_FAST_TOCLIENT) {
+            SCLogError("fast_pattern cannot be used on to_client keyword for "
+                       "bidirectional rule with a streaming buffer to server %u",
+                    s->id);
+            DetectFilesizeFree(de_ctx, fsd);
+            SCReturnInt(-1);
+        }
         s->init_data->init_flags |= SIG_FLAG_INIT_BIDIR_STREAMING_TOSERVER;
     }
     SCReturnInt(0);
diff --git a/src/detect-http-client-body.c b/src/detect-http-client-body.c
index 047b7df2cba..121fd9e3846 100644
--- a/src/detect-http-client-body.c
+++ b/src/detect-http-client-body.c
@@ -168,6 +168,12 @@ static int DetectHttpClientBodySetupSticky(DetectEngineCtx *de_ctx, Signature *s
     if (DetectSignatureSetAppProto(s, ALPROTO_HTTP) < 0)
         return -1;
     // we cannot use a bidirectional rule with a fast pattern to client and this
+    if (s->init_data->init_flags & SIG_FLAG_INIT_BIDIR_FAST_TOCLIENT) {
+        SCLogError("fast_pattern cannot be used on to_client keyword for "
+                   "bidirectional rule with a streaming buffer to server %u",
+                s->id);
+        return -1;
+    }
     s->init_data->init_flags |= SIG_FLAG_INIT_BIDIR_STREAMING_TOSERVER;
     return 0;
 }
diff --git a/src/detect.c b/src/detect.c
index 00edd71e14c..225494bc6c3 100644
--- a/src/detect.c
+++ b/src/detect.c
@@ -1139,7 +1139,7 @@ static bool DetectRunTxInspectRule(ThreadVars *tv,
     do {
         TRACE_SID_TXS(s->id, tx, "engine %p inspect_flags %x", engine, inspect_flags);
         // also if it is not the same direction, but
-        // this is a bidrectional signature, and we are toclient
+        // this is a bidirectional signature, and we are toclient
         if (!(inspect_flags & BIT_U32(engine->id)) &&
                 (direction == engine->dir || ((s->flags & SIG_FLAG_BOTHDIR) && direction == 1))) {