diff --git a/sasmodels/compare.py b/sasmodels/compare.py
index f5228c9b..bf49e8f3 100755
--- a/sasmodels/compare.py
+++ b/sasmodels/compare.py
@@ -551,7 +551,7 @@ def constrain_pars(model_info, pars):
         name = name.split('*')[0]
 
     # Suppress magnetism for python models (not yet implemented)
-    if callable(model_info.Iq):
+    if not model_info.compiled:
         pars.update(suppress_magnetism(pars))
 
     if name == 'barbell':
diff --git a/sasmodels/core.py b/sasmodels/core.py
index 5a35ade9..46cfad68 100644
--- a/sasmodels/core.py
+++ b/sasmodels/core.py
@@ -96,7 +96,7 @@ def _matches(name, kind):
     info = load_model_info(name)
     pars = info.parameters.kernel_parameters
     # TODO: may be adding Fq to the list at some point
-    is_pure_py = callable(info.Iq)
+    is_pure_py = not info.compiled
     if kind == "py":
         return is_pure_py
     elif kind == "c":
@@ -327,7 +327,7 @@ def build_model(model_info, dtype=None, platform="ocl"):
             raise ValueError('unknown mixture type %s'%composition_type)
 
     # If it is a python model, return it immediately
-    if callable(model_info.Iq):
+    if not model_info.compiled:
         from . import kernelpy
         return kernelpy.PyModel(model_info)
 
@@ -364,7 +364,7 @@ def precompile_dlls(path, dtype="double"):
     compiled_dlls = []
     for model_name in list_models():
         model_info = load_model_info(model_name)
-        if not callable(model_info.Iq):
+        if model_info.compiled:
             source = generate.make_source(model_info)['dll']
             old_path = kerneldll.SAS_DLL_PATH
             try:
diff --git a/sasmodels/generate.py b/sasmodels/generate.py
index 13a5ac18..a2454a7a 100644
--- a/sasmodels/generate.py
+++ b/sasmodels/generate.py
@@ -935,9 +935,8 @@ def make_source(model_info):
     Uses source files found in the given search path.  Returns None if this
     is a pure python model, with no C source components.
     """
-    if callable(model_info.Iq):
+    if not model_info.compiled:
         raise ValueError("can't compile python model")
-        #return None
 
     # TODO: need something other than volume to indicate dispersion parameters
     # No volume normalization despite having a volume parameter.
diff --git a/sasmodels/model_test.py b/sasmodels/model_test.py
index 49615ec3..9c1a68b7 100755
--- a/sasmodels/model_test.py
+++ b/sasmodels/model_test.py
@@ -111,10 +111,10 @@ def _add_model_to_suite(loaders, suite, model_info):
     #print('found tests in', model_name)
     #print('------')
 
-    # if ispy then use the dll loader to call pykernel
+    # if is python then use the dll loader to call pykernel
     # don't try to call cl kernel since it will not be
     # available in some environmentes.
-    is_py = callable(model_info.Iq)
+    is_py = not model_info.compiled
 
     # Some OpenCL drivers seem to be flaky, and are not producing the
     # expected result.  Since we don't have known test values yet for
diff --git a/sasmodels/modelinfo.py b/sasmodels/modelinfo.py
index f0032a62..495c74af 100644
--- a/sasmodels/modelinfo.py
+++ b/sasmodels/modelinfo.py
@@ -862,6 +862,7 @@ def isstr(x):
     return isinstance(x, str)
 
 
+# Note: adding 'Fq' even though we can't yet use it to define C code in python.
 #: Set of variables defined in the model that might contain C code
 C_SYMBOLS = ['Imagnetic', 'Iq', 'Iqxy', 'Iqac', 'Iqabc',
              'form_volume', 'shell_volume', 'c_code', 'valid']
@@ -882,8 +883,7 @@ def _find_source_lines(model_info, kernel_module):
     """
     # Only need line numbers if we are creating a C module and the C symbols
     # are defined.
-    if (callable(model_info.Iq)
-            or not any(hasattr(model_info, s) for s in C_SYMBOLS)):
+    if not model_info.compiled:
         return
 
     # load the module source if we can
@@ -966,8 +966,9 @@ def make_model_info(kernel_module):
     info.profile = getattr(kernel_module, 'profile', None) # type: ignore
     info.sesans = getattr(kernel_module, 'sesans', None) # type: ignore
     # Default single and opencl to True for C models.  Python models have callable Iq.
-    info.opencl = getattr(kernel_module, 'opencl', not callable(info.Iq))
-    info.single = getattr(kernel_module, 'single', not callable(info.Iq))
+    info.compiled = not callable(info.Iq) and not callable(info.Fq)
+    info.opencl = getattr(kernel_module, 'opencl', info.compiled)
+    info.single = getattr(kernel_module, 'single', info.compiled)
     info.random = getattr(kernel_module, 'random', None)
     info.hidden = getattr(kernel_module, 'hidden', None) # type: ignore
 
@@ -976,7 +977,7 @@ def make_model_info(kernel_module):
     if control is not None:
         parameters[control].is_control = True
 
-    if callable(info.Iq) and parameters.has_2d:
+    if not info.compiled and parameters.has_2d:
         raise ValueError("oriented python models not supported")
 
     # CRUFT: support old-style ER() for effective radius
@@ -990,7 +991,7 @@ def make_model_info(kernel_module):
     # so just issue a warning if we see ER in a C model.
     ER = getattr(kernel_module, 'ER', None)
     if ER is not None:
-        if callable(info.Iq) and info.radius_effective is None:
+        if not info.compiled and info.radius_effective is None:
             info.radius_effective_modes = ['ER']
             info.radius_effective = lambda mode, *args: ER(*args)
             # TODO: uncomment the following for the sasview 4.3 release
@@ -1093,6 +1094,8 @@ class ModelInfo(object):
     #: the model cannot be run in opencl (e.g., because the model passes
     #: functions by reference), then set this to false.
     opencl = None           # type: bool
+    #: True if the model is compiled with C or OpenCL
+    compiled = None         # type: bool
     #: True if the model is a structure factor used to model the interaction
     #: between form factor models.  This will default to False if it is not
     #: provided in the file.