diff --git a/configure.ac b/configure.ac
index 34b75a768bf..03542a6b1c3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -963,6 +963,7 @@ AS_IF([test $gl_gcc_warnings = no],
 
   if test $emacs_cv_clang = yes; then
     nw="$nw -Wcast-align"
+    nw="$nw -Wdouble-promotion"
   fi
 
   # This causes too much noise in the MinGW build