diff --git a/data/skeletons/lalr1.cc b/data/skeletons/lalr1.cc
index ad37bd27..81ccfbd7 100644
--- a/data/skeletons/lalr1.cc
+++ b/data/skeletons/lalr1.cc
@@ -1155,7 +1155,7 @@ b4_dollar_popdef])[]dnl
 #if ]b4_api_PREFIX[DEBUG
     YYCDEBUG << "LAC: checking lookahead " << yytname_[yytoken] << ':';
 #endif
-    ptrdiff_t lac_top = 0;
+    std::ptrdiff_t lac_top = 0;
     while (true)
       {
         state_type top_state = (yylac_stack_.empty ()
@@ -1194,12 +1194,12 @@ b4_dollar_popdef])[]dnl
         YYCDEBUG << " R" << yyrule - 1;
         // Pop the corresponding number of values from the stack.
         {
-          ptrdiff_t yylen = yyr2_[yyrule];
+          std::ptrdiff_t yylen = yyr2_[yyrule];
           // First pop from the LAC stack as many tokens as possible.
-          ptrdiff_t lac_size = (ptrdiff_t) yylac_stack_.size ();
+          std::ptrdiff_t lac_size = (std::ptrdiff_t) yylac_stack_.size ();
           if (yylen < lac_size)
             {
-              yylac_stack_.resize ((size_t) (lac_size - yylen));
+              yylac_stack_.resize ((std::size_t) (lac_size - yylen));
               yylen = 0;
             }
           else if (lac_size)
@@ -1292,7 +1292,7 @@ b4_error_verbose_if([state_type yystate, const symbol_type& yyla],
   {]b4_error_verbose_if([[
     // Number of reported tokens (one for the "unexpected", one per
     // "expected").
-    ptrdiff_t yycount = 0;
+    std::ptrdiff_t yycount = 0;
     // Its maximum.
     enum { YYERROR_VERBOSE_ARGS_MAXIMUM = 5 };
     // Arguments of yyformat.
@@ -1387,7 +1387,7 @@ b4_error_verbose_if([state_type yystate, const symbol_type& yyla],
 
     std::string yyres;
     // Argument number.
-    ptrdiff_t yyi = 0;
+    std::ptrdiff_t yyi = 0;
     for (char const* yyp = yyformat; *yyp; ++yyp)
       if (yyp[0] == '%' && yyp[1] == 's' && yyi < yycount)
         {
diff --git a/data/skeletons/stack.hh b/data/skeletons/stack.hh
index 1aa89ca1..1fe2b06a 100644
--- a/data/skeletons/stack.hh
+++ b/data/skeletons/stack.hh
@@ -49,7 +49,7 @@ m4_define([b4_stack_define],
         return seq_[size () - 1 - i];
       }
       T&
-      operator[] (ptrdiff_t i)
+      operator[] (std::ptrdiff_t i)
       {
         return operator[] (size_type (i));
       }
@@ -68,7 +68,7 @@ m4_define([b4_stack_define],
         return seq_[size () - 1 - i];
       }
       const T&
-      operator[] (ptrdiff_t i) const
+      operator[] (std::ptrdiff_t i) const
       {
         return operator[] (size_type (i));
       }
@@ -90,7 +90,7 @@ m4_define([b4_stack_define],
 
       /// Pop elements from the stack.
       void
-      pop (ptrdiff_t n = 1) YY_NOEXCEPT
+      pop (std::ptrdiff_t n = 1) YY_NOEXCEPT
       {
         for (; 0 < n; --n)
           seq_.pop_back ();
@@ -109,10 +109,10 @@ m4_define([b4_stack_define],
       {
         return seq_.size ();
       }
-      ptrdiff_t
+      std::ptrdiff_t
       ssize () const YY_NOEXCEPT
       {
-        return (ptrdiff_t) size ();
+        return (std::ptrdiff_t) size ();
       }
 
       /// Iterator on top of the stack (going downwards).
@@ -133,20 +133,20 @@ m4_define([b4_stack_define],
       class slice
       {
       public:
-        slice (const stack& stack, ptrdiff_t range)
+        slice (const stack& stack, std::ptrdiff_t range)
           : stack_ (stack)
           , range_ (range)
         {}
 
         const T&
-        operator[] (ptrdiff_t i) const
+        operator[] (std::ptrdiff_t i) const
         {
           return stack_[range_ - i];
         }
 
       private:
         const stack& stack_;
-        ptrdiff_t range_;
+        std::ptrdiff_t range_;
       };
 
     private: