diff --git a/include/engine/guidance/assemble_route.hpp b/include/engine/guidance/assemble_route.hpp
index 10fca2e42..ff1c905cf 100644
--- a/include/engine/guidance/assemble_route.hpp
+++ b/include/engine/guidance/assemble_route.hpp
@@ -5,7 +5,6 @@
 #include "engine/guidance/route.hpp"
 
 #include <vector>
-#include <numeric>
 
 namespace osrm
 {
@@ -13,21 +12,8 @@ namespace engine
 {
 namespace guidance
 {
-inline Route assembleRoute(const std::vector<RouteLeg> &route_legs)
-{
-    auto distance = std::accumulate(route_legs.begin(), route_legs.end(), 0.,
-                                    [](const double sum, const RouteLeg &leg)
-                                    {
-                                        return sum + leg.distance;
-                                    });
-    auto duration = std::accumulate(route_legs.begin(), route_legs.end(), 0.,
-                                    [](const double sum, const RouteLeg &leg)
-                                    {
-                                        return sum + leg.duration;
-                                    });
 
-    return Route{duration, distance};
-}
+Route assembleRoute(const std::vector<RouteLeg> &route_legs);
 
 } // namespace guidance
 } // namespace engine
diff --git a/src/engine/guidance/assemble_route.cpp b/src/engine/guidance/assemble_route.cpp
new file mode 100644
index 000000000..cdc3a98f2
--- /dev/null
+++ b/src/engine/guidance/assemble_route.cpp
@@ -0,0 +1,30 @@
+#include "engine/guidance/assemble_route.hpp"
+
+#include <numeric>
+
+namespace osrm
+{
+namespace engine
+{
+namespace guidance
+{
+
+Route assembleRoute(const std::vector<RouteLeg> &route_legs)
+{
+    auto distance = std::accumulate(route_legs.begin(), route_legs.end(), 0.,
+                                    [](const double sum, const RouteLeg &leg)
+                                    {
+                                        return sum + leg.distance;
+                                    });
+    auto duration = std::accumulate(route_legs.begin(), route_legs.end(), 0.,
+                                    [](const double sum, const RouteLeg &leg)
+                                    {
+                                        return sum + leg.duration;
+                                    });
+
+    return Route{duration, distance};
+}
+
+} // namespace guidance
+} // namespace engine
+} // namespace osrm