diff --git a/src/api/api_config_params.cpp b/src/api/api_config_params.cpp
index 5b385a872..a04a9f12c 100644
--- a/src/api/api_config_params.cpp
+++ b/src/api/api_config_params.cpp
@@ -37,7 +37,7 @@ extern "C" {
         catch (z3_exception & ex) {
             // The error handler is only available for contexts
             // Just throw a warning.
-            warning_msg(ex.msg());
+            warning_msg("%s", ex.msg());
         }
     }
 
@@ -62,7 +62,7 @@ extern "C" {
         catch (z3_exception & ex) {
             // The error handler is only available for contexts
             // Just throw a warning.
-            warning_msg(ex.msg());
+            warning_msg("%s", ex.msg());
             return Z3_FALSE;
         }
     }
@@ -88,7 +88,7 @@ extern "C" {
         catch (z3_exception & ex) {
             // The error handler is only available for contexts
             // Just throw a warning.
-            warning_msg(ex.msg());
+            warning_msg("%s", ex.msg());
         }
     }
 
diff --git a/src/ast/ast.cpp b/src/ast/ast.cpp
index 507f75482..4e505f977 100644
--- a/src/ast/ast.cpp
+++ b/src/ast/ast.cpp
@@ -1965,7 +1965,7 @@ bool ast_manager::check_sorts(ast const * n) const {
         return true;
     }
     catch (ast_exception & ex) {
-        warning_msg(ex.msg());
+        warning_msg("%s", ex.msg());
         return false;
     }
 }
diff --git a/src/ast/well_sorted.cpp b/src/ast/well_sorted.cpp
index f9f04a2df..cb9ee3f61 100644
--- a/src/ast/well_sorted.cpp
+++ b/src/ast/well_sorted.cpp
@@ -66,7 +66,7 @@ struct well_sorted_proc {
                 strm << "Expected sort: " << mk_pp(expected_sort, m_manager) << "\n";
                 strm << "Actual sort:   " << mk_pp(actual_sort, m_manager) << "\n";
                 strm << "Function sort: " << mk_pp(decl, m_manager) << ".";
-                warning_msg(strm.str().c_str());
+                warning_msg("%s", strm.str().c_str());
                 m_error = true;
                 return;
             }
diff --git a/src/muz/rel/dl_base.cpp b/src/muz/rel/dl_base.cpp
index b7f4d6cef..f79f6c8eb 100644
--- a/src/muz/rel/dl_base.cpp
+++ b/src/muz/rel/dl_base.cpp
@@ -391,7 +391,7 @@ namespace datalog {
             std::ostringstream buffer;
             buffer << "creating large table of size " << upper_bound;
             if (p) buffer << " for relation " << p->get_name();
-            warning_msg(buffer.str().c_str());
+            warning_msg("%s", buffer.str().c_str());
         }
 
         for(table_element i = 0; i < upper_bound; i++) {
diff --git a/src/parsers/smt2/smt2parser.cpp b/src/parsers/smt2/smt2parser.cpp
index 17a931cc3..00f63afd5 100644
--- a/src/parsers/smt2/smt2parser.cpp
+++ b/src/parsers/smt2/smt2parser.cpp
@@ -1034,7 +1034,7 @@ namespace smt2 {
                 else {
                     std::ostringstream str;
                     str << "unknown attribute " << id;
-                    warning_msg(str.str().c_str());
+                    warning_msg("%s", str.str().c_str());
                     next();
                     // just consume the 
                     consume_sexpr();
diff --git a/src/smt/theory_utvpi_def.h b/src/smt/theory_utvpi_def.h
index d5ed4e825..ff295d5a3 100644
--- a/src/smt/theory_utvpi_def.h
+++ b/src/smt/theory_utvpi_def.h
@@ -250,7 +250,7 @@ namespace smt {
             std::stringstream msg;
             msg << "found non utvpi logic expression:\n" << mk_pp(n, get_manager()) << "\n";
             TRACE("utvpi", tout << msg.str(););
-            warning_msg(msg.str().c_str());
+            warning_msg("%s", msg.str().c_str());
             get_context().push_trail(value_trail<context, bool>(m_non_utvpi_exprs));
             m_non_utvpi_exprs = true;
         }
diff --git a/src/util/warning.cpp b/src/util/warning.cpp
index 1105a12f7..ed4cd8725 100644
--- a/src/util/warning.cpp
+++ b/src/util/warning.cpp
@@ -167,4 +167,3 @@ void warning_msg(const char * msg, ...) {
         va_end(args);
     }
 }
-