diff --git a/Makefile b/Makefile
index eae7050ec..5e800db26 100644
--- a/Makefile
+++ b/Makefile
@@ -89,7 +89,7 @@ ifndef AFL_NO_X86
 test_build: afl-gcc afl-as afl-showmap
 	@echo "[*] Testing the CC wrapper and instrumentation output..."
 	unset AFL_USE_ASAN AFL_USE_MSAN; AFL_QUIET=1 AFL_INST_RATIO=100 AFL_PATH=. ./$(TEST_CC) $(CFLAGS) test-instr.c -o test-instr $(LDFLAGS)
-	echo 0 | ./afl-showmap -m none -q -o .test-instr0 ./test-instr
+	./afl-showmap -m none -q -o .test-instr0 ./test-instr < /dev/null
 	echo 1 | ./afl-showmap -m none -q -o .test-instr1 ./test-instr
 	@rm -f test-instr
 	@cmp -s .test-instr0 .test-instr1; DR="$$?"; rm -f .test-instr0 .test-instr1; if [ "$$DR" = "0" ]; then echo; echo "Oops, the instrumentation does not seem to be behaving correctly!"; echo; echo "Please ping <lcamtuf@google.com> to troubleshoot the issue."; echo; exit 1; fi
diff --git a/llvm_mode/Makefile b/llvm_mode/Makefile
index e75958dda..7617f914d 100644
--- a/llvm_mode/Makefile
+++ b/llvm_mode/Makefile
@@ -97,7 +97,9 @@ endif
 test_build: $(PROGS)
 	@echo "[*] Testing the CC wrapper and instrumentation output..."
 	unset AFL_USE_ASAN AFL_USE_MSAN AFL_INST_RATIO; AFL_QUIET=1 AFL_PATH=. AFL_CC=$(CC) ../afl-clang-fast $(CFLAGS) ../test-instr.c -o test-instr $(LDFLAGS)
-	echo 0 | ../afl-showmap -m none -q -o .test-instr0 ./test-instr
+# Use /dev/null to avoid problems with optimization messing up expected
+# branches. See https://github.com/google/AFL/issues/30.
+	../afl-showmap -m none -q -o .test-instr0 ./test-instr < /dev/null
 	echo 1 | ../afl-showmap -m none -q -o .test-instr1 ./test-instr
 	@rm -f test-instr
 	@cmp -s .test-instr0 .test-instr1; DR="$$?"; rm -f .test-instr0 .test-instr1; if [ "$$DR" = "0" ]; then echo; echo "Oops, the instrumentation does not seem to be behaving correctly!"; echo; echo "Please ping <lcamtuf@google.com> to troubleshoot the issue."; echo; exit 1; fi
diff --git a/qemu_mode/build_qemu_support.sh b/qemu_mode/build_qemu_support.sh
index 3199e75bf..06f8b0ca7 100755
--- a/qemu_mode/build_qemu_support.sh
+++ b/qemu_mode/build_qemu_support.sh
@@ -178,6 +178,8 @@ if [ "$ORIG_CPU_TARGET" = "" ]; then
 
   unset AFL_INST_RATIO
 
+  # We shouldn't need the /dev/null hack because program isn't compiled with any
+  # optimizations.
   echo 0 | ./afl-showmap -m none -Q -q -o .test-instr0 ./test-instr || exit 1
   echo 1 | ./afl-showmap -m none -Q -q -o .test-instr1 ./test-instr || exit 1