diff --git a/mozilla/xpcom/libxpt/xptinfo/src/nsXPTParamInfo.cpp b/mozilla/xpcom/libxpt/xptinfo/src/nsXPTParamInfo.cpp
index 3e6515f9177..9aed762a915 100644
--- a/mozilla/xpcom/libxpt/xptinfo/src/nsXPTParamInfo.cpp
+++ b/mozilla/xpcom/libxpt/xptinfo/src/nsXPTParamInfo.cpp
@@ -30,8 +30,6 @@
 #include "xpt_cpp.h"
 #include "xptinfo.h"
 
-// Placeholder - this implementation just returns NULL.
-
 nsIInterfaceInfo*
 nsXPTParamInfo::GetInterface(nsIInterfaceInfo *info) const
 {
@@ -40,7 +38,6 @@ nsXPTParamInfo::GetInterface(nsIInterfaceInfo *info) const
 
     nsInterfaceRecord *record =
         ((nsInterfaceInfo *)info)->getInterfaceRecord();
-
     
     nsIInterfaceInfoManager* mgr;
     if(!(mgr = nsInterfaceInfoManager::GetInterfaceInfoManager()))
@@ -52,7 +49,10 @@ nsXPTParamInfo::GetInterface(nsIInterfaceInfo *info) const
 
     // can't use IID, because it could be null for this entry.
     char *interface_name;
-    interface_name = which_header->interface_directory[type.type.interface].name;
+
+    // offset is 1-based, so subtract 1 to use in interface_directory.
+    interface_name =
+        which_header->interface_directory[type.type.interface - 1].name;
 
     nsIInterfaceInfo *ii;
     nsresult nsr = mgr->GetInfoForName(interface_name, &ii);
@@ -82,7 +82,10 @@ nsXPTParamInfo::GetInterfaceIID(nsIInterfaceInfo *info) const
 
     // can't use IID, because it could be null for this entry.
     char *interface_name;
-    interface_name = which_header->interface_directory[type.type.interface].name;
+
+    // offset is 1-based, so subtract 1 to use in interface_directory.
+    interface_name =
+        which_header->interface_directory[type.type.interface - 1].name;
 
     nsIID* iid;
     nsresult nsr = mgr->GetIIDForName(interface_name, &iid);
diff --git a/mozilla/xpcom/libxpt/xptinfo/tests/TestInterfaceInfo.cpp b/mozilla/xpcom/libxpt/xptinfo/tests/TestInterfaceInfo.cpp
index 70f7ae30de5..c0dc13b08b3 100644
--- a/mozilla/xpcom/libxpt/xptinfo/tests/TestInterfaceInfo.cpp
+++ b/mozilla/xpcom/libxpt/xptinfo/tests/TestInterfaceInfo.cpp
@@ -37,12 +37,14 @@ static void RegAllocator();
 // containing these files.
 
 int main (int argc, char **argv) {
+    int i;
+    nsIID *iid1, *iid2, *iid3, *iid4, *iid5, *iid6;
+    char *name1, *name2, *name3, *name4, *name5, *name6;
+    nsIInterfaceInfo *info1, *info2, *info3, *info4, *info5, *info6;;
+
     RegAllocator();
 
     nsIInterfaceInfoManager *iim = XPTI_GetInterfaceInfoManager();
-    nsIID *iid1, *iid2, *iid3, *iid4;
-    char *name1, *name2, *name3, *name4;
-    nsIInterfaceInfo *info1, *info2, *info3, *info4;
 
     fprintf(stderr, "\ngetting iid for 'nsISupports'\n");
     iim->GetIIDForName("nsISupports", &iid1);
@@ -78,6 +80,45 @@ int main (int argc, char **argv) {
     ((nsInterfaceInfo *)info4)->print(stderr);
 #endif
 
+    fprintf(stderr, "\nparams work?\n");
+    fprintf(stderr, "\ngetting info for name 'nsIServiceManager'\n");
+    iim->GetInfoForName("nsIServiceManager", &info5);
+#ifdef DEBUG
+    ((nsInterfaceInfo *)info5)->print(stderr);
+#endif
+    
+    uint16 methodcount;
+    info5->GetMethodCount(&methodcount);
+    const nsXPTMethodInfo *mi;
+    for (i = 0; i < methodcount; i++) {
+        info5->GetMethodInfo(i, &mi);
+        char *methodname;
+        fprintf(stderr, "method %d, name %s\n", i, mi->GetName());
+    }
+
+    // 7 is GetServiceWithListener, which has juicy params.
+    info5->GetMethodInfo(7, &mi);
+    uint8 paramcount = mi->GetParamCount();
+
+    nsXPTParamInfo param2 = mi->GetParam(2);
+    // should be IID for nsIShutdownListener
+    nsIID *nsISL = param2.GetInterfaceIID(info5);
+    fprintf(stderr, "iid assoc'd with param 2 of method 7 of GetServiceWithListener - %s\n", nsISL->ToString());
+    // if we look up the name?
+    char *nsISLname;
+    iim->GetNameForIID(nsISL, &nsISLname);
+    fprintf(stderr, "which is called %s\n", nsISLname);
+
+    fprintf(stderr, "\nhow about one defined in a different typelib\n");
+    nsXPTParamInfo param3 = mi->GetParam(3);
+    // should be IID for nsIShutdownListener
+    nsIID *nsISS = param3.GetInterfaceIID(info5);
+    fprintf(stderr, "iid assoc'd with param 3 of method 7 of GetServiceWithListener - %s\n", nsISS->ToString());
+    // if we look up the name?
+    char *nsISSname;
+    iim->GetNameForIID(nsISS, &nsISSname);
+    fprintf(stderr, "which is called %s\n", nsISSname);
+
     return 0;
 }    
 
diff --git a/mozilla/xpcom/reflect/xptinfo/src/nsXPTParamInfo.cpp b/mozilla/xpcom/reflect/xptinfo/src/nsXPTParamInfo.cpp
index 3e6515f9177..9aed762a915 100644
--- a/mozilla/xpcom/reflect/xptinfo/src/nsXPTParamInfo.cpp
+++ b/mozilla/xpcom/reflect/xptinfo/src/nsXPTParamInfo.cpp
@@ -30,8 +30,6 @@
 #include "xpt_cpp.h"
 #include "xptinfo.h"
 
-// Placeholder - this implementation just returns NULL.
-
 nsIInterfaceInfo*
 nsXPTParamInfo::GetInterface(nsIInterfaceInfo *info) const
 {
@@ -40,7 +38,6 @@ nsXPTParamInfo::GetInterface(nsIInterfaceInfo *info) const
 
     nsInterfaceRecord *record =
         ((nsInterfaceInfo *)info)->getInterfaceRecord();
-
     
     nsIInterfaceInfoManager* mgr;
     if(!(mgr = nsInterfaceInfoManager::GetInterfaceInfoManager()))
@@ -52,7 +49,10 @@ nsXPTParamInfo::GetInterface(nsIInterfaceInfo *info) const
 
     // can't use IID, because it could be null for this entry.
     char *interface_name;
-    interface_name = which_header->interface_directory[type.type.interface].name;
+
+    // offset is 1-based, so subtract 1 to use in interface_directory.
+    interface_name =
+        which_header->interface_directory[type.type.interface - 1].name;
 
     nsIInterfaceInfo *ii;
     nsresult nsr = mgr->GetInfoForName(interface_name, &ii);
@@ -82,7 +82,10 @@ nsXPTParamInfo::GetInterfaceIID(nsIInterfaceInfo *info) const
 
     // can't use IID, because it could be null for this entry.
     char *interface_name;
-    interface_name = which_header->interface_directory[type.type.interface].name;
+
+    // offset is 1-based, so subtract 1 to use in interface_directory.
+    interface_name =
+        which_header->interface_directory[type.type.interface - 1].name;
 
     nsIID* iid;
     nsresult nsr = mgr->GetIIDForName(interface_name, &iid);
diff --git a/mozilla/xpcom/reflect/xptinfo/tests/TestInterfaceInfo.cpp b/mozilla/xpcom/reflect/xptinfo/tests/TestInterfaceInfo.cpp
index 70f7ae30de5..c0dc13b08b3 100644
--- a/mozilla/xpcom/reflect/xptinfo/tests/TestInterfaceInfo.cpp
+++ b/mozilla/xpcom/reflect/xptinfo/tests/TestInterfaceInfo.cpp
@@ -37,12 +37,14 @@ static void RegAllocator();
 // containing these files.
 
 int main (int argc, char **argv) {
+    int i;
+    nsIID *iid1, *iid2, *iid3, *iid4, *iid5, *iid6;
+    char *name1, *name2, *name3, *name4, *name5, *name6;
+    nsIInterfaceInfo *info1, *info2, *info3, *info4, *info5, *info6;;
+
     RegAllocator();
 
     nsIInterfaceInfoManager *iim = XPTI_GetInterfaceInfoManager();
-    nsIID *iid1, *iid2, *iid3, *iid4;
-    char *name1, *name2, *name3, *name4;
-    nsIInterfaceInfo *info1, *info2, *info3, *info4;
 
     fprintf(stderr, "\ngetting iid for 'nsISupports'\n");
     iim->GetIIDForName("nsISupports", &iid1);
@@ -78,6 +80,45 @@ int main (int argc, char **argv) {
     ((nsInterfaceInfo *)info4)->print(stderr);
 #endif
 
+    fprintf(stderr, "\nparams work?\n");
+    fprintf(stderr, "\ngetting info for name 'nsIServiceManager'\n");
+    iim->GetInfoForName("nsIServiceManager", &info5);
+#ifdef DEBUG
+    ((nsInterfaceInfo *)info5)->print(stderr);
+#endif
+    
+    uint16 methodcount;
+    info5->GetMethodCount(&methodcount);
+    const nsXPTMethodInfo *mi;
+    for (i = 0; i < methodcount; i++) {
+        info5->GetMethodInfo(i, &mi);
+        char *methodname;
+        fprintf(stderr, "method %d, name %s\n", i, mi->GetName());
+    }
+
+    // 7 is GetServiceWithListener, which has juicy params.
+    info5->GetMethodInfo(7, &mi);
+    uint8 paramcount = mi->GetParamCount();
+
+    nsXPTParamInfo param2 = mi->GetParam(2);
+    // should be IID for nsIShutdownListener
+    nsIID *nsISL = param2.GetInterfaceIID(info5);
+    fprintf(stderr, "iid assoc'd with param 2 of method 7 of GetServiceWithListener - %s\n", nsISL->ToString());
+    // if we look up the name?
+    char *nsISLname;
+    iim->GetNameForIID(nsISL, &nsISLname);
+    fprintf(stderr, "which is called %s\n", nsISLname);
+
+    fprintf(stderr, "\nhow about one defined in a different typelib\n");
+    nsXPTParamInfo param3 = mi->GetParam(3);
+    // should be IID for nsIShutdownListener
+    nsIID *nsISS = param3.GetInterfaceIID(info5);
+    fprintf(stderr, "iid assoc'd with param 3 of method 7 of GetServiceWithListener - %s\n", nsISS->ToString());
+    // if we look up the name?
+    char *nsISSname;
+    iim->GetNameForIID(nsISS, &nsISSname);
+    fprintf(stderr, "which is called %s\n", nsISSname);
+
     return 0;
 }