diff --git a/odc/geo/_blocks.py b/odc/geo/_blocks.py
index cc78b0b..db8f484 100644
--- a/odc/geo/_blocks.py
+++ b/odc/geo/_blocks.py
@@ -13,9 +13,15 @@
 from .types import Chunks2d
 
 
-def _find_common_type(array_types, scalar_types):
-    # TODO: don't use find_common_type as it's being removed from numpy
-    return np.find_common_type(array_types, scalar_types)
+def _find_common_type(array_types, scalar_type=None):
+    if scalar_type is None:
+        return np.result_type(*array_types)
+    else:
+        if np.issubdtype(scalar_type, np.floating):
+            array_types = array_types + [0.0]
+        elif np.issubdtype(scalar_type, np.complexfloating):
+            array_types = array_types + [0j]
+        return np.result_type(*array_types)
 
 
 class BlockAssembler:
@@ -33,7 +39,7 @@ def __init__(
         self._dtype = (
             np.dtype("float32")
             if len(blocks) == 0
-            else _find_common_type([b.dtype for b in blocks.values()], [])
+            else _find_common_type([b.dtype for b in blocks.values()])
         )
         self._axis = axis
         self._blocks = blocks
@@ -126,7 +132,8 @@ def extract(
             dtype = self._dtype
             if fill_value is not None:
                 # possibly upgrade to float based on fill_value
-                dtype = _find_common_type([dtype], [np.min_scalar_type(fill_value)])
+                fill_dtype = np.min_scalar_type(fill_value)
+                dtype = _find_common_type([dtype], np.min_scalar_type(fill_value))
         else:
             dtype = np.dtype(dtype)