diff --git a/grpc.spec b/grpc.spec
index fbe5779..1a3f51c 100644
--- a/grpc.spec
+++ b/grpc.spec
@@ -27,6 +27,7 @@ Patch0: grpc-0001-enforce-system-crypto-policies.patch
 Patch2: grpc-0003-use-shell-loop-instead-makefile-function.patch
 Patch3: 99f8a10aec994a8957fbb6787768b444ef34d6a2.patch
 Patch4: 72351f63fd650cc7acfcd2d0307e8e8e8f777283.patch
+Patch5: remove-gnu99.patch
 
 %description
 gRPC is a modern open source high performance RPC framework that can run in any
@@ -85,6 +86,7 @@ Python3 bindings for gRPC library.
 %patch2 -p1
 %patch3 -p1
 %patch4 -p1
+%patch5 -p1
 sed -i 's:^prefix ?= .*:prefix ?= %{_prefix}:' Makefile
 sed -i 's:$(prefix)/lib:$(prefix)/%{_lib}:' Makefile
 sed -i 's:^GTEST_LIB =.*::' Makefile
diff --git a/remove-gnu99.patch b/remove-gnu99.patch
new file mode 100644
index 0000000..dbea5d6
--- /dev/null
+++ b/remove-gnu99.patch
@@ -0,0 +1,12 @@
+diff -ruN grpc-1.26.0.orig/setup.py grpc-1.26.0/setup.py
+--- grpc-1.26.0.orig/setup.py	2019-12-18 02:29:27.000000000 +0100
++++ grpc-1.26.0/setup.py	2020-12-09 08:41:38.202678255 +0100
+@@ -179,7 +179,7 @@
+       # available dynamically
+       EXTRA_ENV_COMPILE_ARGS += ' /MT'
+   elif "linux" in sys.platform:
+-    EXTRA_ENV_COMPILE_ARGS += ' -std=gnu99 -fvisibility=hidden -fno-wrapv -fno-exceptions'
++    EXTRA_ENV_COMPILE_ARGS += ' -fvisibility=hidden -fno-wrapv -fno-exceptions'
+   elif "darwin" in sys.platform:
+     EXTRA_ENV_COMPILE_ARGS += ' -stdlib=libc++ -fvisibility=hidden -fno-wrapv -fno-exceptions'
+