diff --git a/src/tools/generators/archive-generator.jam b/src/tools/generators/archive-generator.jam
index 1b8721802..6afc8e7aa 100644
--- a/src/tools/generators/archive-generator.jam
+++ b/src/tools/generators/archive-generator.jam
@@ -52,7 +52,7 @@ class archive-generator : generator
         {
             for local t in $(sources)
             {
-                if [ type.is-derived [ $(t).type ] LIB ]
+                if [ $(t).type ] && [ type.is-derived [ $(t).type ] LIB ]
                 {
                     usage-requirements += <library>$(t) ;
                 }
diff --git a/src/tools/generators/linking-generator.jam b/src/tools/generators/linking-generator.jam
index 23d0c1e8c..37277a0b2 100644
--- a/src/tools/generators/linking-generator.jam
+++ b/src/tools/generators/linking-generator.jam
@@ -53,7 +53,7 @@ class linking-generator : generator
         local extra-xdll-paths ;
         for local s in $(sources)
         {
-            if [ type.is-derived [ $(s).type ] SHARED_LIB ] && ! [ $(s).action ]
+            if [ $(s).type ] && [ type.is-derived [ $(s).type ] SHARED_LIB ] && ! [ $(s).action ]
             {
                 local location = [ path.root [ $(s).name ]
                     [ $(s).path ] ] ;
@@ -143,7 +143,7 @@ class linking-generator : generator
         local fst ;
         for local s in $(sources)
         {
-            if [ type.is-derived [ $(s).type ] SEARCHED_LIB ]
+            if [ $(s).type ] && [ type.is-derived [ $(s).type ] SEARCHED_LIB ]
             {
                 local name = [ $(s).name ] ;
                 if [ $(s).shared ]