diff --git a/src/api/api_opt.cpp b/src/api/api_opt.cpp
index afb7d25c4..65be0de0a 100644
--- a/src/api/api_opt.cpp
+++ b/src/api/api_opt.cpp
@@ -141,7 +141,7 @@ extern "C" {
             }
             catch (z3_exception& ex) {
                 r = l_undef;
-                if (ex.msg() == "canceled" && mk_c(c)->m().canceled()) {
+                if (ex.msg() == std::string("canceled") && mk_c(c)->m().canceled()) {
                     to_optimize_ptr(o)->set_reason_unknown(ex.msg());
                 }
                 else {
diff --git a/src/opt/opt_parse.cpp b/src/opt/opt_parse.cpp
index 758379517..666f79d97 100644
--- a/src/opt/opt_parse.cpp
+++ b/src/opt/opt_parse.cpp
@@ -577,7 +577,7 @@ private:
         
     symbol const& peek(unsigned i) { return tok.peek(i); }
 
-    bool try_accept(char * token) {
+    bool try_accept(char const * token) {
         if (peek(0) == token) {
             tok.next();
             return true;
diff --git a/src/util/file_path.h b/src/util/file_path.h
index 8a2d053d8..ee0f3d620 100644
--- a/src/util/file_path.h
+++ b/src/util/file_path.h
@@ -19,6 +19,8 @@ Revision History:
 #ifndef FILE_PATH_H_
 #define FILE_PATH_H_
 
+#include<string.h>
+
 inline char const * get_extension(char const * file_name) {
     if (file_name == 0)
         return 0;