diff --git a/src/analyses/custom_bitvector_analysis.cpp b/src/analyses/custom_bitvector_analysis.cpp
index be96ce1e2c2..cf19a7aa895 100644
--- a/src/analyses/custom_bitvector_analysis.cpp
+++ b/src/analyses/custom_bitvector_analysis.cpp
@@ -330,7 +330,8 @@ void custom_bitvector_domaint::transform(
             unsigned bit_nr=
               cba.get_bit_nr(code_function_call.arguments()[1]);
 
-            modet mode;
+            // initialize to make Visual Studio happy
+            modet mode = modet::SET_MUST;
 
             if(identifier=="__CPROVER_set_must")
               mode=modet::SET_MUST;
@@ -458,7 +459,8 @@ void custom_bitvector_domaint::transform(
         unsigned bit_nr=
           cba.get_bit_nr(instruction.code.op1());
 
-        modet mode;
+        // initialize to make Visual Studio happy
+        modet mode = modet::SET_MUST;
 
         if(statement=="set_must")
           mode=modet::SET_MUST;
diff --git a/src/goto-diff/change_impact.cpp b/src/goto-diff/change_impact.cpp
index e9e00bab388..1e916a5250a 100644
--- a/src/goto-diff/change_impact.cpp
+++ b/src/goto-diff/change_impact.cpp
@@ -571,7 +571,7 @@ void change_impactt::output_change_impact(
     const unsigned mod_flags=
       c_entry==c_i.end() ? SAME : c_entry->second;
 
-    char prefix;
+    char prefix = ' ';
     // syntactic changes are preferred over data/control-dependence
     // modifications
     if(mod_flags==SAME)
@@ -639,7 +639,7 @@ void change_impactt::output_change_impact(
     const unsigned mod_flags=
       c_entry==n_c_i.end() ? SAME : c_entry->second;
 
-    char prefix;
+    char prefix = ' ';
     // syntactic changes are preferred over data/control-dependence
     // modifications
     if(mod_flags==SAME)
@@ -691,7 +691,7 @@ void change_impactt::output_change_impact(
     const unsigned old_mod_flags=
       o_c_entry==o_c_i.end() ? SAME : o_c_entry->second;
 
-    char prefix;
+    char prefix = ' ';
     // syntactic changes are preferred over data/control-dependence
     // modifications
     if(old_mod_flags==SAME)
diff --git a/src/goto-programs/remove_const_function_pointers.cpp b/src/goto-programs/remove_const_function_pointers.cpp
index eefaf90d77f..2c2a0144583 100644
--- a/src/goto-programs/remove_const_function_pointers.cpp
+++ b/src/goto-programs/remove_const_function_pointers.cpp
@@ -398,7 +398,7 @@ bool remove_const_function_pointerst::try_resolve_expression(
   exprt simplified_expr=simplify_expr(expr, ns);
   bool resolved;
   expressionst resolved_expressions;
-  bool is_resolved_expression_const;
+  bool is_resolved_expression_const = false;
   if(simplified_expr.id()==ID_index)
   {
     const index_exprt &index_expr=to_index_expr(simplified_expr);