diff --git a/src/lib/time/formats.hpp b/src/lib/time/formats.hpp
index 5136dcf64..daea02508 100644
--- a/src/lib/time/formats.hpp
+++ b/src/lib/time/formats.hpp
@@ -107,7 +107,7 @@ namespace time {
     class Seconds
       : public Format
       {
-        TimeFract secs_;
+        
       };
     
     
diff --git a/src/lib/time/lumitime.cpp b/src/lib/time/lumitime.cpp
index 0aeacf9fb..c1837667b 100644
--- a/src/lib/time/lumitime.cpp
+++ b/src/lib/time/lumitime.cpp
@@ -43,7 +43,7 @@ namespace time {
      *  into the internal time scale used by GAVL and Lumiera internal time values.
      */
     inline gavl_time_t
-    rational2time (TimeFract const& fractionalSeconds)
+    rational2time (FSecs const& fractionalSeconds)
     {
       return boost::rational_cast<gavl_time_t> (GAVL_TIME_SCALE * fractionalSeconds);
     }
@@ -77,7 +77,7 @@ namespace time {
    *  from a fraction of seconds, given as rational number.
    *  An example would be to the time unit of a framerate.
    */
-  Time::Time (TimeFract const& fractionalSeconds)
+  Time::Time (FSecs const& fractionalSeconds)
     : TimeValue(rational2time (fractionalSeconds))
     { }
   
diff --git a/src/lib/time/quantiser.hpp b/src/lib/time/quantiser.hpp
index 29ab6d9b8..1d7ea45e9 100644
--- a/src/lib/time/quantiser.hpp
+++ b/src/lib/time/quantiser.hpp
@@ -62,7 +62,7 @@ namespace time {
     {
       
     public:
-      FixedFrameQuantiser (TimeFract frames_per_second);
+      FixedFrameQuantiser (FSecs frames_per_second);
     };
   
   
diff --git a/src/lib/time/timevalue.hpp b/src/lib/time/timevalue.hpp
index 9f2888588..674952ace 100644
--- a/src/lib/time/timevalue.hpp
+++ b/src/lib/time/timevalue.hpp
@@ -183,8 +183,9 @@ namespace time {
   
   /* ======= specific Time entities ==================== */
   
-  /** rational representation of fractional seconds */
-  typedef boost::rational<gavl_time_t> TimeFract;
+  /** rational representation of fractional seconds
+   * @warning do not mix up gavl_time_t and FSecs */
+  typedef boost::rational<long> FSecs;
 
   /**
    * Lumiera's internal time value datatype.
@@ -223,7 +224,7 @@ namespace time {
         : TimeValue(calcResult)
         { }
       
-      Time (TimeFract const& fractionalSeconds);
+      Time (FSecs const& fractionalSeconds);
       
       Time ( long millis
            , uint secs 
diff --git a/src/proc/asset/meta/time-grid.cpp b/src/proc/asset/meta/time-grid.cpp
index 15745ec0c..c1ab270e8 100644
--- a/src/proc/asset/meta/time-grid.cpp
+++ b/src/proc/asset/meta/time-grid.cpp
@@ -117,14 +117,14 @@ namespace meta {
   /* === TimeGrid shortcut builder functions === */
   
   PGrid
-  TimeGrid::build (Symbol gridID, TimeFract frames_per_second)
+  TimeGrid::build (Symbol gridID, FSecs frames_per_second)
   {
     return build (gridID,frames_per_second, Time(0));
   }
   
   
   PGrid
-  TimeGrid::build (Symbol gridID, TimeFract frames_per_second, Time origin)
+  TimeGrid::build (Symbol gridID, FSecs frames_per_second, Time origin)
   {
     UNIMPLEMENTED ("build a trivial time grid");
   }
diff --git a/src/proc/asset/meta/time-grid.hpp b/src/proc/asset/meta/time-grid.hpp
index cc28e8806..1e449a372 100644
--- a/src/proc/asset/meta/time-grid.hpp
+++ b/src/proc/asset/meta/time-grid.hpp
@@ -59,7 +59,7 @@ namespace meta {
   using lib::Symbol;
   using lib::time::Time;
   using lib::time::TimeValue;
-  using lib::time::TimeFract;
+  using lib::time::FSecs;
   
   
   class TimeGrid;
@@ -80,8 +80,8 @@ namespace meta {
       // TODO define the TimeGrid API here
       
       /* === shortcut builder functions === */
-      static PGrid build (Symbol gridID, TimeFract frames_per_second);
-      static PGrid build (Symbol gridID, TimeFract frames_per_second, Time origin);
+      static PGrid build (Symbol gridID, FSecs frames_per_second);
+      static PGrid build (Symbol gridID, FSecs frames_per_second, Time origin);
       
     protected:
       TimeGrid (EntryID<TimeGrid> const&);
@@ -94,7 +94,7 @@ namespace meta {
   template<>
   struct Builder<TimeGrid>
     {
-      TimeFract fps_;
+      FSecs fps_;
       Time      origin_;
       
       /** when building a compound or variable grid,
diff --git a/tests/components/proc/asset/meta/time-grid-basics-test.cpp b/tests/components/proc/asset/meta/time-grid-basics-test.cpp
index 36f5e8c62..c85fe2b95 100644
--- a/tests/components/proc/asset/meta/time-grid-basics-test.cpp
+++ b/tests/components/proc/asset/meta/time-grid-basics-test.cpp
@@ -66,7 +66,7 @@ namespace test {
   namespace { // Test definitions...
     
     Time testOrigin (12,23);
-    TimeFract testFps (5,4);
+    FSecs testFps (5,4);
     
   }
   
diff --git a/tests/lib/time/time-quantisation-test.cpp b/tests/lib/time/time-quantisation-test.cpp
index 1513ab8fa..22325c37e 100644
--- a/tests/lib/time/time-quantisation-test.cpp
+++ b/tests/lib/time/time-quantisation-test.cpp
@@ -81,8 +81,8 @@ namespace test{
           FrameNr count(qVal);                      // materialise this quantised time into..
           int n = count;                            // frame count, accessible as plain number
           
-          CHECK (TimeFract(n-1, 25) < org);         // verify quantisation: the original time
-          CHECK (org < TimeFract(n+1, 25));         // is properly bracketed by (n-1, n+2)
+          CHECK (Time(FSecs(n-1, 25)) < org);       // verify quantisation: the original time
+          CHECK (org < Time(FSecs(n+1, 25)));       // is properly bracketed by (n-1, n+2)
         }
       
       
@@ -116,7 +116,7 @@ namespace test{
       void
       checkMultipleGrids (TimeValue org)
         {
-          TimeGrid::build("my_alternate_grid", TimeFract(30000,1001));
+          TimeGrid::build("my_alternate_grid", FSecs(30000,1001));
           
           QuTime palVal (org, "my_simple_grid");
           QuTime ntscVal (org, "my_alternate_grid");