diff --git a/cli/pathmatch.h b/cli/pathmatch.h
index b7880a77c..e35228233 100644
--- a/cli/pathmatch.h
+++ b/cli/pathmatch.h
@@ -37,7 +37,7 @@ public:
      * @param caseSensitive Match the case of the characters when
      *   matching paths?
      */
-    PathMatch(const std::vector<std::string> &masks, bool caseSensitive = true);
+    explicit PathMatch(const std::vector<std::string> &masks, bool caseSensitive = true);
 
     /**
      * @brief Match path against list of masks.
diff --git a/lib/checkio.cpp b/lib/checkio.cpp
index 8b0424f4a..16ff14a44 100644
--- a/lib/checkio.cpp
+++ b/lib/checkio.cpp
@@ -88,7 +88,7 @@ struct Filepointer {
     unsigned int op_indent;
     enum AppendMode { UNKNOWN_AM, APPEND, APPEND_EX };
     AppendMode append_mode;
-    Filepointer(OpenMode mode_ = UNKNOWN_OM)
+    explicit Filepointer(OpenMode mode_ = UNKNOWN_OM)
         : mode(mode_), mode_indent(0), lastOperation(NONE), op_indent(0), append_mode(UNKNOWN_AM) {
     }
 };
diff --git a/lib/checkunusedvar.cpp b/lib/checkunusedvar.cpp
index 6f02fcf20..23a71d071 100644
--- a/lib/checkunusedvar.cpp
+++ b/lib/checkunusedvar.cpp
@@ -40,12 +40,12 @@ public:
     /** Store information about variable usage */
     class VariableUsage {
     public:
-        VariableUsage(const Variable *var = nullptr,
-                      VariableType type = standard,
-                      bool read = false,
-                      bool write = false,
-                      bool modified = false,
-                      bool allocateMemory = false) :
+        explicit VariableUsage(const Variable *var = nullptr,
+                               VariableType type = standard,
+                               bool read = false,
+                               bool write = false,
+                               bool modified = false,
+                               bool allocateMemory = false) :
             _var(var),
             _lastAccess(var?var->nameToken():0),
             _type(type),
diff --git a/lib/tokenlist.cpp b/lib/tokenlist.cpp
index cf265e01f..271b28d19 100644
--- a/lib/tokenlist.cpp
+++ b/lib/tokenlist.cpp
@@ -427,7 +427,7 @@ struct AST_state {
     unsigned int depth;
     unsigned int inArrayAssignment;
     bool cpp;
-    AST_state(bool cpp_) : depth(0), inArrayAssignment(0), cpp(cpp_) {}
+    explicit AST_state(bool cpp_) : depth(0), inArrayAssignment(0), cpp(cpp_) {}
 };
 
 static bool iscast(const Token *tok)