diff --git a/SoObjects/SOGo/LDAPSource.m b/SoObjects/SOGo/LDAPSource.m
index 94d8f4c6b..e9fa32e28 100644
--- a/SoObjects/SOGo/LDAPSource.m
+++ b/SoObjects/SOGo/LDAPSource.m
@@ -22,6 +22,7 @@
 
 #import <Foundation/NSArray.h>
 #import <Foundation/NSDictionary.h>
+#import <Foundation/NSLock.h>
 #import <Foundation/NSString.h>
 #import <Foundation/NSUserDefaults.h>
 
@@ -41,6 +42,10 @@ static NSString *LDAPContactInfoAttribute = nil;
 static int timeLimit;
 static int sizeLimit;
 
+#if defined(THREADSAFE)
+static NSLock *lock;
+#endif
+
 @implementation LDAPSource
 
 + (void) initialize
@@ -126,6 +131,10 @@ static int sizeLimit;
 				    @"calFBURL", @"proxyAddresses",
 				    nil];	
       [commonSearchFields retain];
+
+#if defined(THREADSAFE)
+      lock = [NSLock new];
+#endif
     }
 }
 
@@ -312,6 +321,10 @@ static int sizeLimit;
   NSString *userDN;
   NGLdapConnection *bindConnection;
 
+#if defined(THREADSAFE)
+  [lock lock];
+#endif
+
   didBind = NO;
 
   if ([loginToCheck length] > 0)
@@ -337,6 +350,10 @@ static int sizeLimit;
       [bindConnection release];
     }
 
+#if defined(THREADSAFE)
+  [lock unlock];
+#endif
+
   return didBind;
 }
 
@@ -431,6 +448,10 @@ static int sizeLimit;
   NGLdapEntry *currentEntry;
   NSString *value;
 
+#if defined(THREADSAFE)
+  [lock lock];
+#endif
+
   ids = [NSMutableArray array];
 
   if ([self _initLDAPConnection])
@@ -455,6 +476,10 @@ static int sizeLimit;
 
   [ldapConnection autorelease];
 
+#if defined(THREADSAFE)
+  [lock unlock];
+#endif
+
   return ids;
 }
 
@@ -552,6 +577,10 @@ static int sizeLimit;
   NGLdapEntry *currentEntry;
   NSEnumerator *entries;
 
+#if defined(THREADSAFE)
+  [lock lock];
+#endif
+
   contacts = [NSMutableArray array];
 
   if ([match length] > 0)
@@ -571,6 +600,10 @@ static int sizeLimit;
       [ldapConnection release];
     }
 
+#if defined(THREADSAFE)
+  [lock unlock];
+#endif
+
   return contacts;
 }
 
@@ -579,6 +612,10 @@ static int sizeLimit;
   NSDictionary *contactEntry;
   NGLdapEntry *ldapEntry;
 
+#if defined(THREADSAFE)
+  [lock lock];
+#endif
+
   contactEntry = nil;
 
   if ([entryID length] > 0)
@@ -597,6 +634,10 @@ static int sizeLimit;
       [ldapConnection autorelease];
     }
 
+#if defined(THREADSAFE)
+  [lock unlock];
+#endif
+
   return contactEntry;
 }
 
@@ -607,6 +648,10 @@ static int sizeLimit;
   NSEnumerator *entries;
   EOQualifier *qualifier;
 
+#if defined(THREADSAFE)
+  [lock lock];
+#endif
+
   contactEntry = nil;
 
   if ([uid length] > 0)
@@ -628,6 +673,10 @@ static int sizeLimit;
       [ldapConnection release];
     }
 
+#if defined(THREADSAFE)
+  [lock unlock];
+#endif
+
   return contactEntry;
 }