diff --git a/deepspeech/modules/subsampling.py b/deepspeech/modules/subsampling.py
index 5aa2fd8eacdafeff7829f19bc220749ed76b33c2..0edc6ee5c10481e558b48fb11af5d7d371451af2 100644
--- a/deepspeech/modules/subsampling.py
+++ b/deepspeech/modules/subsampling.py
@@ -128,7 +128,7 @@ class Conv2dSubsampling4(BaseSubsampling):
         """
         x = x.unsqueeze(1)  # (b, c=1, t, f)
         x = self.conv(x)
-        b, c, t, f = paddle.shape(x)
+        b, c, t, f = x.shape
         x = self.out(x.transpose([0, 2, 1, 3]).reshape([b, t, c * f]))
         x, pos_emb = self.pos_enc(x, offset)
         return x, pos_emb, x_mask[:, :, :-2:2][:, :, :-2:2]
@@ -181,7 +181,7 @@ class Conv2dSubsampling6(BaseSubsampling):
         """
         x = x.unsqueeze(1)  # (b, c, t, f)
         x = self.conv(x)
-        b, c, t, f = paddle.shape(x)
+        b, c, t, f = x.shape
         x = self.linear(x.transpose([0, 2, 1, 3]).reshape([b, t, c * f]))
         x, pos_emb = self.pos_enc(x, offset)
         return x, pos_emb, x_mask[:, :, :-2:2][:, :, :-4:3]