diff --git a/configure.in b/configure.in
index bdaf6a58020..ac2697a1bb2 100644
--- a/configure.in
+++ b/configure.in
@@ -1255,11 +1255,6 @@ if test "$GNU_CC"; then
         fi
     fi
     WARNINGS_AS_ERRORS='-Werror'
-    # Don't treat -Wuninitialized as error b/c it has lots of false positives.
-    WARNINGS_AS_ERRORS="$WARNINGS_AS_ERRORS -Wno-error=uninitialized"
-    # Don't treat -Wdeprecated-declarations as error b/c we don't want our
-    # builds held hostage when a platform-specific API is suddenly deprecated.
-    WARNINGS_AS_ERRORS="$WARNINGS_AS_ERRORS -Wno-error=deprecated-declarations"
     DSO_CFLAGS=''
     DSO_PIC_CFLAGS='-fPIC'
     ASFLAGS="$ASFLAGS -fPIC"
@@ -6998,6 +6993,15 @@ MOZ_ARG_ENABLE_BOOL(warnings-as-errors,
     MOZ_ENABLE_WARNINGS_AS_ERRORS=)
 if test -z "$MOZ_ENABLE_WARNINGS_AS_ERRORS"; then
    WARNINGS_AS_ERRORS=''
+elif test "$GNU_CC"; then
+    # Prevent the following GCC warnings from being treated as errors:
+    # -Wuninitialized - too many false positives
+    # -Wdeprecated-declarations - we don't want our builds held hostage when a
+    #   platform-specific API becomes deprecated.
+    MOZ_C_SUPPORTS_WARNING(-W, no-error=uninitialized, ac_c_has_noerror_uninitialized)
+    MOZ_CXX_SUPPORTS_WARNING(-W, no-error=uninitialized, ac_cxx_has_noerror_uninitialized)
+    MOZ_C_SUPPORTS_WARNING(-W, no-error=deprecated-declarations, ac_c_has_noerror_deprecated_declarations)
+    MOZ_CXX_SUPPORTS_WARNING(-W, no-error=deprecated-declarations, ac_cxx_has_noerror_deprecated_declarations)
 fi
 
 dnl ========================================================
diff --git a/js/src/configure.in b/js/src/configure.in
index e7790d09dca..e3bae3cf45e 100644
--- a/js/src/configure.in
+++ b/js/src/configure.in
@@ -1066,11 +1066,6 @@ if test "$GNU_CC"; then
         fi
     fi
     WARNINGS_AS_ERRORS='-Werror'
-    # Don't treat -Wuninitialized as error b/c it has lots of false positives.
-    WARNINGS_AS_ERRORS="$WARNINGS_AS_ERRORS -Wno-error=uninitialized"
-    # Don't treat -Wdeprecated-declarations as error b/c we don't want our
-    # builds held hostage when a platform-specific API is suddenly deprecated.
-    WARNINGS_AS_ERRORS="$WARNINGS_AS_ERRORS -Wno-error=deprecated-declarations"
     DSO_CFLAGS=''
     DSO_PIC_CFLAGS='-fPIC'
     ASFLAGS="$ASFLAGS -fPIC"
@@ -3265,6 +3260,15 @@ MOZ_ARG_DISABLE_BOOL(warnings-as-errors,
     MOZ_ENABLE_WARNINGS_AS_ERRORS=)
 if test -z "$MOZ_ENABLE_WARNINGS_AS_ERRORS"; then
    WARNINGS_AS_ERRORS=''
+elif test "$GNU_CC"; then
+    # Prevent the following GCC warnings from being treated as errors:
+    # -Wuninitialized - too many false positives
+    # -Wdeprecated-declarations - we don't want our builds held hostage when a
+    #   platform-specific API becomes deprecated.
+    MOZ_C_SUPPORTS_WARNING(-W, no-error=uninitialized, ac_c_has_noerror_uninitialized)
+    MOZ_CXX_SUPPORTS_WARNING(-W, no-error=uninitialized, ac_cxx_has_noerror_uninitialized)
+    MOZ_C_SUPPORTS_WARNING(-W, no-error=deprecated-declarations, ac_c_has_noerror_deprecated_declarations)
+    MOZ_CXX_SUPPORTS_WARNING(-W, no-error=deprecated-declarations, ac_cxx_has_noerror_deprecated_declarations)
 fi
 
 dnl ========================================================