diff --git a/src/compiler/glsl/glcpp/glcpp.c b/src/compiler/glsl/glcpp/glcpp.c
index f08b14427f4..b90a46e7769 100644
--- a/src/compiler/glsl/glcpp/glcpp.c
+++ b/src/compiler/glsl/glcpp/glcpp.c
@@ -102,6 +102,7 @@ load_text_file(void *ctx, const char *filename)
 static void
 init_fake_gl_context (struct gl_context *gl_ctx)
 {
+	memset(gl_ctx, 0, sizeof(*gl_ctx));
 	gl_ctx->API = API_OPENGL_COMPAT;
 	gl_ctx->Const.DisableGLSLLineContinuations = false;
 }