diff --git a/src/engine/execcmd.h b/src/engine/execcmd.h
index 783415f2b..938e577ad 100644
--- a/src/engine/execcmd.h
+++ b/src/engine/execcmd.h
@@ -16,6 +16,7 @@
 #ifndef EXECCMD_H
 #define EXECCMD_H
 
+#include "strings.h"
 #include <time.h>
 
 typedef struct timing_info
@@ -37,7 +38,7 @@ typedef void (* ExecCmdCallback)
 
 void exec_cmd
 (
-    char const * command,
+    string const * command,
     ExecCmdCallback func,
     void * closure,
     LIST * shell,
diff --git a/src/engine/execnt.c b/src/engine/execnt.c
index efcfd1e5d..816e66c05 100644
--- a/src/engine/execnt.c
+++ b/src/engine/execnt.c
@@ -66,7 +66,7 @@ int maxline();
 /* bump intr to note command interruption */
 static void onintr( int );
 /* trim leading and trailing whitespace */
-void string_new_trimmed( string * pResult, char const * source );
+void string_new_trimmed( string * pResult, string const * source );
 /* is the command suitable for direct execution via CreateProcessA() */
 static long can_spawn( string * pCommand );
 /* add two 64-bit unsigned numbers, h1l1 and h2l2 */
@@ -188,7 +188,7 @@ void execnt_unit_test()
 
 void exec_cmd
 (
-    char const * command_orig,
+    string const * pCommand_orig,
     ExecCmdCallback func,
     void * closure,
     LIST * shell,
@@ -211,7 +211,7 @@ void exec_cmd
     }
 
     /* Trim all leading and trailing leading whitespace. */
-    string_new_trimmed( &command_local, command_orig );
+    string_new_trimmed( &command_local, pCommand_orig );
 
     /* Check to see if we need to hack around the line-length limitation. Look
      * for a JAMSHELL setting of "%", indicating that the command should be
@@ -441,7 +441,7 @@ void exec_cmd
             string_free( &cmdtab[ slot ].target );
             string_new ( &cmdtab[ slot ].target );
         }
-        string_copy( &cmdtab[ slot ].command, command_orig );
+        string_copy( &cmdtab[ slot ].command, pCommand_orig->value );
 
         /* CreateProcessA() Windows API places a limit of 32768 characters
          * (bytes) on the allowed command-line length, including a trailing
@@ -629,12 +629,13 @@ int maxline()
  * value needs to be released using string_free().
  */
 
-void string_new_trimmed( string * pResult, char const * source )
+void string_new_trimmed( string * pResult, string const * pSource )
 {
+    char const * source = pSource->value;
     int source_len;
     while ( isspace( *source ) )
         ++source;
-    source_len = strlen( source );
+    source_len = pSource->size - ( source - pSource->value );
     while ( ( source_len > 0 ) && isspace( source[ source_len - 1 ] ) )
         --source_len;
     string_new( pResult );
diff --git a/src/engine/execunix.c b/src/engine/execunix.c
index 0ab7dff6e..3150d84df 100644
--- a/src/engine/execunix.c
+++ b/src/engine/execunix.c
@@ -9,6 +9,7 @@
 #include "lists.h"
 #include "execcmd.h"
 #include "output.h"
+#include "strings.h"
 #include <errno.h>
 #include <signal.h>
 #include <stdio.h>
@@ -115,7 +116,7 @@ void onintr( int disp )
 
 void exec_cmd
 (
-    char const * command,
+    string const * pCommand,
     ExecCmdCallback func,
     void * closure,
     LIST * shell,
@@ -157,7 +158,7 @@ void exec_cmd
         {
             switch ( object_str( list_item( iter ) )[0] )
             {
-                case '%': argv[ i ] = command; ++gotpercent; break;
+                case '%': argv[ i ] = pCommand->value; ++gotpercent; break;
                 case '!': argv[ i ] = jobno; break;
                 default : argv[ i ] = object_str( list_item( iter ) );
             }
@@ -166,7 +167,7 @@ void exec_cmd
         }
 
         if ( !gotpercent )
-        argv[ i++ ] = command;
+        argv[ i++ ] = pCommand->value;
 
         argv[ i ] = 0;
     }
@@ -174,7 +175,7 @@ void exec_cmd
     {
         argv[ 0 ] = "/bin/sh";
         argv[ 1 ] = "-c";
-        argv[ 2 ] = command;
+        argv[ 2 ] = pCommand->value;
         argv[ 3 ] = 0;
     }
 
@@ -182,8 +183,8 @@ void exec_cmd
     ++cmdsrunning;
 
     /* Save off actual command string. */
-    cmdtab[ slot ].command = BJAM_MALLOC_ATOMIC( strlen( command ) + 1 );
-    strcpy( cmdtab[ slot ].command, command );
+    cmdtab[ slot ].command = BJAM_MALLOC_ATOMIC( pCommand->size + 1 );
+    strcpy( cmdtab[ slot ].command, pCommand->value );
 
     /* Initialize only once. */
     if ( !initialized )
diff --git a/src/engine/make1.c b/src/engine/make1.c
index 07d213d07..9a6773419 100644
--- a/src/engine/make1.c
+++ b/src/engine/make1.c
@@ -554,8 +554,8 @@ static void make1c( state * pState )
         {
             /* Pop state first because exec_cmd() could push state. */
             pop_state( &state_stack );
-            exec_cmd( cmd->buf->value, make_closure, pState->t, cmd->shell,
-                rule_name, target );
+            exec_cmd( cmd->buf, make_closure, pState->t, cmd->shell, rule_name,
+                target );
         }
     }
     else