diff --git a/configure b/configure
index 40aa64f413..b0fcc0a008 100755
--- a/configure
+++ b/configure
@@ -5074,7 +5074,7 @@ elif is_in -static $cc $LDFLAGS && ! is_in --static $pkg_config $pkg_config_flag
 Note: When building a static binary, add --pkg-config-flags=\"--static\"."
 fi
 
-if test $doxygen != $doxygen_default && \
+if test "$doxygen" != "$doxygen_default" && \
   ! $doxygen --version >/dev/null 2>&1; then
     warn "Specified doxygen \"$doxygen\" not found, API documentation will fail to build."
 fi
@@ -7631,7 +7631,7 @@ if enabled makeinfo_command; then
   [ 0$($makeinfo --version | grep "texinfo" | sed 's/.*texinfo[^0-9]*\([0-9]*\)\..*/\1/') -ge 5 ] \
     && enable makeinfo_html || disable makeinfo_html
 else
-  if test $makeinfo != $makeinfo_default ; then
+  if test "$makeinfo" != "$makeinfo_default" ; then
     warn "Specified makeinfo \"$makeinfo\" not found."
   fi
 fi