diff --git a/src/HDF5.jl b/src/HDF5.jl
index 8cadcea25..fda612aad 100644
--- a/src/HDF5.jl
+++ b/src/HDF5.jl
@@ -1936,14 +1936,6 @@ function __init__()
     __init_globals__()
     register_blosc()
 
-    # Generate the Float16 datatype:
-    float16 = h5t_copy(H5T.NATIVE_FLOAT)
-    h5t_set_fields(float16, 15, 10, 5, 0, 10)
-    h5t_set_size(float16, 2)
-    h5t_set_ebias(float16, 15)
-    h5t_lock(float16)
-    H5T.NATIVE_FLOAT16 = float16
-
     # Turn off automatic error printing
     # h5e_set_auto(H5E.DEFAULT, C_NULL, C_NULL)
 
diff --git a/src/api_types.jl b/src/api_types.jl
index 1cdb81639..2f2db615d 100644
--- a/src/api_types.jl
+++ b/src/api_types.jl
@@ -414,5 +414,13 @@ function __init_globals__()
     H5T.NATIVE_FLOAT    = read_const(:H5T_NATIVE_FLOAT_g)
     H5T.NATIVE_DOUBLE   = read_const(:H5T_NATIVE_DOUBLE_g)
 
+    # Defines a type corresponding to Julia's IEEE Float16 type.
+    float16 = h5t_copy(H5T.NATIVE_FLOAT)
+    h5t_set_fields(float16, 15, 10, 5, 0, 10)
+    h5t_set_size(float16, 2)
+    h5t_set_ebias(float16, 15)
+    h5t_lock(float16)
+    H5T.NATIVE_FLOAT16 = float16
+
     nothing
 end
diff --git a/src/macros.jl b/src/macros.jl
index a8f029724..8a0856aeb 100644
--- a/src/macros.jl
+++ b/src/macros.jl
@@ -54,13 +54,13 @@ macro defconstants(prefix::Symbol, expr::Expr)
 
         isruntime = isexpr(line, :(=)) ? false :
                     isexpr(line, :(::)) ? true :
-                    error("Unexpected statement: ", repr(line))
+                    error("Unexpected statement: ", line)
 
         # Get the name and type pair
         nametype = isruntime ? line : line.args[1]
-        isexpr(nametype, :(::)) || error("Expected `name::type`, got ", repr(nametype))
+        isexpr(nametype, :(::)) || error("Expected `name::type`, got: ", nametype)
         name = nametype.args[1]::Symbol
-        type = nametype.args[2]
+        type = nametype.args[2]::Union{Symbol,Expr}
         # Save type for later use
         push!(imports, type)
 
@@ -106,12 +106,14 @@ macro defconstants(prefix::Symbol, expr::Expr)
         end
         function Base.getproperty(::$einnermod.$prefix, sym::Symbol)
             $(getbody...)
+            error($(string(prefix) * " has no constant "), sym)
         end
     end
     if !isempty(setbody)
         setfn = quote
             function Base.setproperty!(::$einnermod.$prefix, sym::Symbol, value)
                 $(setbody...)
+                error($(string(prefix) * "."), sym, " cannot be set")
             end
         end
         append!(block.args, Base.remove_linenums!(setfn).args)