diff --git a/config.mak.dev b/config.mak.dev
index 40eddf16ee..9906065b15 100644
--- a/config.mak.dev
+++ b/config.mak.dev
@@ -21,7 +21,7 @@ endif
 endif
 
 ifneq ($(uname_S),FreeBSD)
-ifneq ($(or $(filter gcc6,$(COMPILER_FEATURES)),$(filter clang7,$(COMPILER_FEATURES))),)
+ifneq ($(filter gcc6,$(COMPILER_FEATURES)),)
 ifndef USE_MIMALLOC
 DEVELOPER_CFLAGS += -std=gnu99
 endif
@@ -29,6 +29,9 @@ endif
 else
 # FreeBSD cannot limit to C99 because its system headers unconditionally
 # rely on C11 features.
+#
+# Clang cannot limit to C99 when using glibc 2.43 because its system headers
+# depend on the _Generic C11 feature. This works with GCC though.
 endif
 
 DEVELOPER_CFLAGS += -Wdeclaration-after-statement