diff --git a/configure b/configure
index 110a3fd4ae..b9707c5638 100755
--- a/configure
+++ b/configure
@@ -4229,6 +4229,9 @@ probe_libc(){
     elif check_${pfx}cpp_condition sys/brand.h "defined LABELED_BRAND_NAME"; then
         eval ${pfx}libc_type=solaris
         add_${pfx}cppflags -D__EXTENSIONS__ -D_XOPEN_SOURCE=600
+    # FFmpeg needs a POSIX.1-2001/XSI compliant C library
+    else
+        add_${pfx}cppflags -D_XOPEN_SOURCE=600
     fi
 }