diff --git a/config.m4 b/config.m4
index 8f6aa432784..53ffe8ffaac 100644
--- a/config.m4
+++ b/config.m4
@@ -1039,8 +1039,8 @@ if test "$PHP_GRPC" != "no"; then
     -DOPENSSL_NO_ASM -D_GNU_SOURCE -DWIN32_LEAN_AND_MEAN \
     -D_HAS_EXCEPTIONS=0 -DNOMINMAX -DGRPC_ARES=0 \
     -DGRPC_POSIX_FORK_ALLOW_PTHREAD_ATFORK=1 \
-    -DGRPC_XDS_USER_AGENT_SUFFIX="\"PHP\"" \
-    -DGRPC_XDS_USER_AGENT_VERSION_SUFFIX="\"1.39.0dev\"")
+    -DGRPC_XDS_USER_AGENT_NAME_SUFFIX='"\"PHP\""' \
+    -DGRPC_XDS_USER_AGENT_VERSION_SUFFIX='"\"1.39.0dev\""')
 
   PHP_ADD_BUILD_DIR($ext_builddir/src/core/ext/filters/census)
   PHP_ADD_BUILD_DIR($ext_builddir/src/core/ext/filters/client_channel)
diff --git a/templates/config.m4.template b/templates/config.m4.template
index 48a8b776300..ad694511370 100644
--- a/templates/config.m4.template
+++ b/templates/config.m4.template
@@ -61,8 +61,8 @@
       -DOPENSSL_NO_ASM -D_GNU_SOURCE -DWIN32_LEAN_AND_MEAN ${"\\"}
       -D_HAS_EXCEPTIONS=0 -DNOMINMAX -DGRPC_ARES=0 ${"\\"}
       -DGRPC_POSIX_FORK_ALLOW_PTHREAD_ATFORK=1 ${"\\"}
-      -DGRPC_XDS_USER_AGENT_SUFFIX="\"PHP\"" ${"\\"}
-      -DGRPC_XDS_USER_AGENT_VERSION_SUFFIX="\"${settings.php_version.php()}\"")
+      -DGRPC_XDS_USER_AGENT_NAME_SUFFIX='"\"PHP\""' ${"\\"}
+      -DGRPC_XDS_USER_AGENT_VERSION_SUFFIX='"\"${settings.php_version.php()}\""')
   <%
     dirs = sorted(set(src[:src.rfind('/')] for src in srcs))
   %>