diff --git a/repos/dde_rump/include/util/allocator_fap.h b/repos/dde_rump/include/util/allocator_fap.h
index ba559add5..3f75526a4 100644
--- a/repos/dde_rump/include/util/allocator_fap.h
+++ b/repos/dde_rump/include/util/allocator_fap.h
@@ -21,8 +21,8 @@
 #include <rump/env.h>
 
 namespace Allocator {
-	template <unsigned VM_SIZE, typename POLICY> class Backend_alloc;
-	template <unsigned VM_SIZE, typename POLICY> class Fap;
+	template <unsigned long VM_SIZE, typename POLICY> class Backend_alloc;
+	template <unsigned long VM_SIZE, typename POLICY> class Fap;
 }
 
 
@@ -48,7 +48,7 @@ namespace Allocator {
 	/**
 	 * Back-end allocator for Genode's slab allocator
 	 */
-	template <unsigned VM_SIZE, typename POLICY = Default_allocator_policy>
+	template <unsigned long VM_SIZE, typename POLICY = Default_allocator_policy>
 	class Backend_alloc : public Genode::Allocator,
 	                      public Genode::Rm_connection,
 	                      public Genode::Region_map_client
@@ -56,7 +56,7 @@ namespace Allocator {
 		private:
 
 			enum {
-				BLOCK_SIZE = 1024  * 1024,         /* 1 MB */
+				BLOCK_SIZE = 2 * 1024  * 1024,     /* 2 MB */
 				ELEMENTS   = VM_SIZE / BLOCK_SIZE, /* MAX number of dataspaces in VM */
 			};
 
@@ -193,7 +193,7 @@ namespace Allocator {
 	/**
 	 * Interface
 	 */
-	template <unsigned VM_SIZE, typename POLICY = Default_allocator_policy>
+	template <unsigned long VM_SIZE, typename POLICY = Default_allocator_policy>
 	class Fap
 	{
 		private:
diff --git a/repos/dde_rump/src/lib/rump/hypercall.cc b/repos/dde_rump/src/lib/rump/hypercall.cc
index fef8a934c..b8e8e38c4 100644
--- a/repos/dde_rump/src/lib/rump/hypercall.cc
+++ b/repos/dde_rump/src/lib/rump/hypercall.cc
@@ -22,7 +22,10 @@
 #include <util/random.h>
 #include <util/string.h>
 
-enum { SUPPORTED_RUMP_VERSION = 17 };
+enum {
+	SUPPORTED_RUMP_VERSION = 17,
+	MAX_VIRTUAL_MEMORY = (sizeof(void *) == 4 ? 256UL : 4096UL) * 1024 * 1024
+};
 
 static bool verbose = false;
 
@@ -170,6 +173,7 @@ int rumpuser_getparam(const char *name, void *buf, size_t buflen)
 		}
 
 		rump_ram -= RESERVE_MEM;
+		rump_ram  = Genode::min((unsigned long)MAX_VIRTUAL_MEMORY, rump_ram);
 
 		/* convert to string */
 		Genode::snprintf((char *)buf, buflen, "%zu", rump_ram);
@@ -233,7 +237,7 @@ struct Allocator_policy
 };
 
 
-typedef Allocator::Fap<128 * 1024 * 1024, Allocator_policy> Rump_alloc;
+typedef Allocator::Fap<MAX_VIRTUAL_MEMORY, Allocator_policy> Rump_alloc;
 
 static Genode::Lock & alloc_lock()
 {