diff --git a/gawk.spec b/gawk.spec
index e43dea6..1614a44 100644
--- a/gawk.spec
+++ b/gawk.spec
@@ -191,8 +191,8 @@ makeinfo --html -I doc -o html/gawkinet doc/gawkinet.texi
 make check
 
 # Check we have correctly specified the ABI version for the current sources:
-api_major_vers=$(grep -e "gawk_api_major.*[[:digit:]]" gawkapi.h | grep -o -e "[[:digit:]]")
-api_minor_vers=$(grep -e "gawk_api_minor.*[[:digit:]]" gawkapi.h | grep -o -e "[[:digit:]]")
+api_major_vers=$(grep -i -e "gawk_api_major.*[[:digit:]]" gawkapi.h | grep -o -e "[[:digit:]]")
+api_minor_vers=$(grep -i -e "gawk_api_minor.*[[:digit:]]" gawkapi.h | grep -o -e "[[:digit:]]")
 
 if [[ "$api_major_vers" != %{gawk_api_major} || "$api_minor_vers" != %{gawk_api_minor} ]]; then
   echo "Build Error: specified gawk(abi) version [%{gawk_api_major}.%{gawk_api_minor}] is different than source code API version [$api_major_vers.$api_minor_vers]!" >&2