diff --git a/src/cli/cli_coap.cpp b/src/cli/cli_coap.cpp
index 3c118aa26..a6ba7bc8f 100644
--- a/src/cli/cli_coap.cpp
+++ b/src/cli/cli_coap.cpp
@@ -260,7 +260,7 @@ exit:
 ThreadError Coap::ProcessClient(int argc, char *argv[])
 {
     ThreadError error = kThreadError_None;
-    otMessage *message = otCoapNewMessage(sInstance, NULL);
+    otMessage *message = NULL;
     otMessageInfo messageInfo;
     otCoapHeader header;
 
diff --git a/src/core/api/coap_api.cpp b/src/core/api/coap_api.cpp
index d54c9fe35..2ea2dff84 100644
--- a/src/core/api/coap_api.cpp
+++ b/src/core/api/coap_api.cpp
@@ -126,7 +126,11 @@ const otCoapOption *otCoapHeaderGetNextOption(otCoapHeader *aHeader)
 
 otMessage *otCoapNewMessage(otInstance *aInstance, const otCoapHeader *aHeader)
 {
-    return aInstance->mThreadNetif.GetCoapClient().NewMessage(*(static_cast<const Coap::Header *>(aHeader)));
+    Message *message;
+    VerifyOrExit(aHeader != NULL, message = NULL);
+    message = aInstance->mThreadNetif.GetCoapClient().NewMessage(*(static_cast<const Coap::Header *>(aHeader)));
+exit:
+    return message;
 }
 
 ThreadError otCoapSendRequest(otInstance *aInstance, otMessage *aMessage, const otMessageInfo *aMessageInfo,