diff --git a/configure.ac b/configure.ac
index 86b89c280a..8253ae7085 100644
--- a/configure.ac
+++ b/configure.ac
@@ -396,7 +396,25 @@ dnl Checks for typedefs, structures, and compiler characteristics.
 AC_TYPE_SIZE_T
 
 dnl Checks for library functions.
-AC_CHECK_FUNCS([getenv getopt getopt_long mkdir setenv strdup strncpy strcpy snprintf sprintf vsnprintf gmtime_r statvfs localtime_r lstat inet_aton rand_r])
+AC_CHECK_FUNCS([m4_normalize([
+  getenv
+  getopt
+  getopt_long
+  mkdir
+  setenv
+  strdup
+  strncpy
+  strcpy
+  snprintf
+  sprintf
+  vsnprintf
+  gmtime_r
+  statvfs
+  localtime_r
+  lstat
+  inet_aton
+  rand_r
+])])
 
 dnl Find out how to get struct tm
 AC_STRUCT_TM
diff --git a/libgphoto2_port/configure.ac b/libgphoto2_port/configure.ac
index 9777110ca9..81265ce276 100644
--- a/libgphoto2_port/configure.ac
+++ b/libgphoto2_port/configure.ac
@@ -239,9 +239,15 @@ mt.mnt_mountp;
 ])
 
 
-
 dnl Checks for library functions.
-AC_CHECK_FUNCS([setmntent endmntent strerror snprintf vsnprintf flock])
+AC_CHECK_FUNCS([m4_normalize([
+  setmntent
+  endmntent
+  strerror
+  snprintf
+  vsnprintf
+  flock
+])])
 
 dnl Check if TIOCM_RTS is included in one of several possible files
 gp_found_tiocm_rts=no