diff --git a/scripts/genconfig.sh b/scripts/genconfig.sh
index 07fec2c..b50c32b 100755
--- a/scripts/genconfig.sh
+++ b/scripts/genconfig.sh
@@ -35,10 +35,15 @@
     #endif
 EOF
 
-  # Hard to come by in uClibc.
+  # Work around some uClibc limitations
   probesymbol TOYBOX_ICONV -c << EOF
     #include "iconv.h"
 EOF
+  probesymbol TOYBOX_FALLOCATE << EOF
+    #include <fcntl.h>
+
+    int main(int argc, char *argv[]) { return posix_fallocate(0,0,0); }
+EOF
 }
 
 genconfig()