diff --git a/grpc.spec b/grpc.spec
index 66cf4a5..b78efc3 100644
--- a/grpc.spec
+++ b/grpc.spec
@@ -126,14 +126,17 @@ This subpackage contains source code of the gRPC reference implementation.
 
 %prep
 %autosetup -N
+find "." -type f -exec grep -l '/usr/bin/env' {} + | \
+	xargs -r perl -i -lpe 's{#! ?/usr/bin/env python\S+}{#!/usr/bin/python3}g'
+find "." -type f -exec grep -l '/usr/bin/env ' {} + | \
+	xargs -r perl -i -lpe 's{#! ?/usr/bin/env }{#!/usr/bin/}g'
 pushd third_party/xxhash
 %patch1 -p1
 %patch2 -p1
 popd
 rm -Rf third_party/abseil-cpp/
-find . -type f -exec grep -l '#!/usr/bin/env py' | \
-	xargs perl -i -lpe 's{#!/usr/bin/env py\w+}{#!/usr/bin/python3}g'
 
+%build
 # protoc is invoked strangely; make it happy with this dir or it will assert()
 mkdir -p third_party/protobuf/src