diff --git a/src/test/ex.cpp b/src/test/ex.cpp
index 829386112eb..276385e4b87 100644
--- a/src/test/ex.cpp
+++ b/src/test/ex.cpp
@@ -28,14 +28,14 @@ class ex1 : public ex {
     char const * m_msg;
 public:
     ex1(char const * m):m_msg(m) {}
-    char const * what() const override { return m_msg; }
+    char const * what() const noexcept override { return m_msg; }
 };
 
 class ex2 : public ex {
     std::string m_msg;
 public:
     ex2(char const * m):m_msg(m) {}
-    char const * what() const override { return m_msg.c_str(); }
+    char const * what() const noexcept override { return m_msg.c_str(); }
 };
 
 static void th() {
diff --git a/src/util/z3_exception.cpp b/src/util/z3_exception.cpp
index 8c08308ae58..2d7c589f75a 100644
--- a/src/util/z3_exception.cpp
+++ b/src/util/z3_exception.cpp
@@ -35,7 +35,7 @@ z3_error::z3_error(unsigned error_code):m_error_code(error_code) {
     SASSERT(error_code != 0); 
 }
 
-char const * z3_error::what() const {
+char const * z3_error::what() const noexcept {
     switch (m_error_code) {
     case ERR_MEMOUT: return "out of memory";
     case ERR_TIMEOUT: return "timeout";
@@ -67,6 +67,6 @@ default_exception::default_exception(fmt, char const* msg, ...) {
     m_msg = out.str();
 }
 
-char const * default_exception::what() const { 
+char const * default_exception::what() const noexcept { 
     return m_msg.c_str(); 
 }
diff --git a/src/util/z3_exception.h b/src/util/z3_exception.h
index a31ac89cd42..0a2bf1186e9 100644
--- a/src/util/z3_exception.h
+++ b/src/util/z3_exception.h
@@ -32,7 +32,7 @@ class z3_error : public z3_exception {
     unsigned m_error_code;
 public:
     z3_error(unsigned error_code);
-    char const * what() const override;
+    char const * what() const noexcept override;
     unsigned error_code() const override;
 };
 
@@ -42,6 +42,6 @@ class default_exception : public z3_exception {
     struct fmt {};
     default_exception(std::string && msg) : m_msg(std::move(msg)) {}
     default_exception(fmt, char const* msg, ...);
-    char const * what() const override;
+    char const * what() const noexcept override;
 };