diff --git a/src/coord.jl b/src/coord.jl
index b1880c9..4c0997a 100644
--- a/src/coord.jl
+++ b/src/coord.jl
@@ -93,7 +93,11 @@ function Transformation(
     ctx::Ptr{PJ_CONTEXT}=C_NULL
 )
     pj = proj_create(pipeline, ctx)
-    @assert !Bool(proj_is_crs(pj)) "Not a transformation (but a CRS):\n$pipeline"
+    if Bool(proj_is_crs(pj))
+        throw(ArgumentError("""Cannot create a Transformation from a single CRS.
+        Pass either one pipeline or a source and target CRS.
+        CRS given: $(repr(pipeline))"""))
+    end
     pj = always_xy ? normalize_axis_order!(pj; ctx) : pj
     return Transformation(pj, direction)
 end
diff --git a/test/libproj.jl b/test/libproj.jl
index 3da1f80..c5da2ad 100644
--- a/test/libproj.jl
+++ b/test/libproj.jl
@@ -166,7 +166,7 @@ end
     @test inv(PJ_IDENT) == PJ_IDENT
     @test inv(PJ_INV) == PJ_FWD
 
-    @test_throws AssertionError Proj.Transformation("EPSG:28992")
+    @test_throws ArgumentError Proj.Transformation("EPSG:28992")
     trans = Proj.Transformation("+proj=pipeline +ellps=GRS80 +step +proj=merc +step +proj=axisswap +order=2,1")
 
 end