diff --git a/man/rgbasm.1 b/man/rgbasm.1
index 32cbd469d..10e82ec55 100644
--- a/man/rgbasm.1
+++ b/man/rgbasm.1
@@ -291,6 +291,13 @@ This warning is enabled by
 Warn when shifting macro arguments past their limits.
 This warning is enabled by
 .Fl Wextra .
+.It Fl Wno-nested-comment
+Warn when the block comment start sequence
+.Ql /*
+is found inside of a block comment.
+Block comments cannot be nested, so an "inner"
+.Ql */
+is likely to have ended the whole comment.
 .It Fl Wno-obsolete
 Warn when obsolete constructs such as the
 .Ic _PI
diff --git a/src/asm/warning.cpp b/src/asm/warning.cpp
index 8869f56e6..7baede8ff 100644
--- a/src/asm/warning.cpp
+++ b/src/asm/warning.cpp
@@ -191,6 +191,7 @@ static uint8_t const _wextraCommands[] = {
 static uint8_t const _weverythingCommands[] = {
     WARNING_BACKWARDS_FOR,
     WARNING_BUILTIN_ARG,
+    WARNING_CHARMAP_REDEF,
     WARNING_DIV,
     WARNING_EMPTY_DATA_DIRECTIVE,
     WARNING_EMPTY_MACRO_ARG,
diff --git a/test/asm/multiple-charmaps.err b/test/asm/multiple-charmaps.err
index 65eeef8c3..511e28963 100644
--- a/test/asm/multiple-charmaps.err
+++ b/test/asm/multiple-charmaps.err
@@ -2,6 +2,8 @@ warning: multiple-charmaps.asm(46) -> multiple-charmaps.asm::print_mapped(34): [
     Treating multi-unit strings as numbers is deprecated
 warning: multiple-charmaps.asm(54) -> multiple-charmaps.asm::print_mapped(34): [-Wobsolete]
     Treating multi-unit strings as numbers is deprecated
+warning: multiple-charmaps.asm(64): [-Wcharmap-redef]
+    Overriding charmap mapping
 warning: multiple-charmaps.asm(73) -> multiple-charmaps.asm::print_mapped(34): [-Wobsolete]
     Treating multi-unit strings as numbers is deprecated
 warning: multiple-charmaps.asm(95) -> multiple-charmaps.asm::print_mapped(34): [-Wobsolete]
diff --git a/test/asm/pushc-without-switch.asm b/test/asm/pushc-without-switch.asm
index 7209c3998..690cb43c2 100644
--- a/test/asm/pushc-without-switch.asm
+++ b/test/asm/pushc-without-switch.asm
@@ -1,5 +1,6 @@
 ; Triggering a charmap realloc while the charmap has been pushed onto the stack used
 ; to induce a use-after-free.
+opt Wno-charmap-redef
 pushc
 charmap "000000000000000000000000000000000",12
 popc