diff --git a/config.mak.dev b/config.mak.dev
index 8830b78c1b552f..eecb12c1111ff4 100644
--- a/config.mak.dev
+++ b/config.mak.dev
@@ -21,15 +21,12 @@ endif
 endif
 
 ifneq ($(uname_S),FreeBSD)
-ifneq ($(filter gcc6,$(COMPILER_FEATURES)),)
+ifneq ($(or $(filter gcc6,$(COMPILER_FEATURES)),$(filter clang7,$(COMPILER_FEATURES))),)
 DEVELOPER_CFLAGS += -std=gnu99
 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
@@ -101,6 +98,13 @@ endif
 endif
 endif
 
+# glibc 2.43 headers unconditionally use _Generic even when we ask the
+# compiler to stick to -std=gnu99 and unlike GCC, clang lacks a
+# workaround to squelch warnings from system headers.
+ifneq ($(filter clang1,$(COMPILER_FEATURES)),)     # if we are using clang
+DEVELOPER_CFLAGS += -Wno-c11-extensions
+endif
+
 # https://bugzilla.redhat.com/show_bug.cgi?id=2075786
 ifneq ($(filter gcc12,$(COMPILER_FEATURES)),)
 DEVELOPER_CFLAGS += -Wno-error=stringop-overread