diff --git a/capn.h b/capn.h
index cf9cedb..acb42ad 100644
--- a/capn.h
+++ b/capn.h
@@ -16,6 +16,8 @@ extern "C" {
 #define CAPN_INLINE static
 #endif
 
+#define CAPN_VERSION 1
+
 /* struct capn is a common structure shared between segments in the same
  * session/context so that far pointers between segments will be created.
  *
diff --git a/compiler/c++.capnp.h b/compiler/c++.capnp.h
index dfb34ac..babead7 100644
--- a/compiler/c++.capnp.h
+++ b/compiler/c++.capnp.h
@@ -3,6 +3,11 @@
 /* AUTO GENERATED - DO NOT EDIT */
 #include <capn.h>
 
+#if CAPN_VERSION != 1
+#error "version mismatch between capn.h and generated code"
+#endif
+
+
 #ifdef __cplusplus
 extern "C" {
 #endif
diff --git a/compiler/capnpc-c.c b/compiler/capnpc-c.c
index 61404bf..1868ac0 100644
--- a/compiler/capnpc-c.c
+++ b/compiler/capnpc-c.c
@@ -1152,7 +1152,10 @@ int main() {
 		str_addf(&HDR, "#ifndef CAPN_%X%X\n", (uint32_t) (file_node->n.id >> 32), (uint32_t) file_node->n.id);
 		str_addf(&HDR, "#define CAPN_%X%X\n", (uint32_t) (file_node->n.id >> 32), (uint32_t) file_node->n.id);
 		str_addf(&HDR, "/* AUTO GENERATED - DO NOT EDIT */\n");
-		str_addf(&HDR, "#include <capn.h>\n");
+		str_addf(&HDR, "#include <capn.h>\n\n");
+		str_addf(&HDR, "#if CAPN_VERSION != 1\n");
+		str_addf(&HDR, "#error \"version mismatch between capn.h and generated code\"\n");
+		str_addf(&HDR, "#endif\n\n");
 
 		capn_resolve(&file_req.imports.p);
 
diff --git a/compiler/schema.capnp.h b/compiler/schema.capnp.h
index e3c47a3..6443f90 100644
--- a/compiler/schema.capnp.h
+++ b/compiler/schema.capnp.h
@@ -2,6 +2,11 @@
 #define CAPN_A93FC509624C72D9
 /* AUTO GENERATED - DO NOT EDIT */
 #include <capn.h>
+
+#if CAPN_VERSION != 1
+#error "version mismatch between capn.h and generated code"
+#endif
+
 #include "c++.capnp.h"
 
 #ifdef __cplusplus
diff --git a/compiler/test.capnp.h b/compiler/test.capnp.h
index f5165a2..98ea44e 100644
--- a/compiler/test.capnp.h
+++ b/compiler/test.capnp.h
@@ -2,6 +2,11 @@
 #define CAPN_D508EEBDC2DC42B8
 /* AUTO GENERATED - DO NOT EDIT */
 #include <capn.h>
+
+#if CAPN_VERSION != 1
+#error "version mismatch between capn.h and generated code"
+#endif
+
 #include "c++.capnp.h"
 
 #ifdef __cplusplus