diff --git a/lib/std/encoding/base64.c3 b/lib/std/encoding/base64.c3
index 1b962cd8b..4c9cf4ee0 100644
--- a/lib/std/encoding/base64.c3
+++ b/lib/std/encoding/base64.c3
@@ -220,7 +220,7 @@ fn usz! Base64Decoder.decode(&self, char[] src, char[] dst)
 
 	if (trailing == 0) return dn;
 
-	src = src[^trailing:];
+	src = src[^trailing..];
 	char c0 = self.reverse[src[0]];
 	char c1 = self.reverse[src[1]];
 	if (c0 == self.invalid || c1 == self.invalid) return Base64Error.INVALID_PADDING?;
diff --git a/releasenotes.md b/releasenotes.md
index 5b0775018..a32b6a834 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -56,6 +56,7 @@
 - Default visibility can be overridden per module compile unit. Eg `module foo @private`.
 - Optimized macro codegen for -O0.
 - Addition of unary `+`.
+- Remove possibility to elide length when using ':' for slices.
 - Remove the `:` and `;` used in $if, $switch etc.
 - Faults have an ordinal.
 - Generic module contracts.
diff --git a/src/compiler/parse_expr.c b/src/compiler/parse_expr.c
index a6071c618..f9577dd67 100644
--- a/src/compiler/parse_expr.c
+++ b/src/compiler/parse_expr.c
@@ -30,6 +30,7 @@ bool parse_current_is_expr(ParseContext *c)
  */
 bool parse_range(ParseContext *c, Range *range)
 {
+	SourceSpan start = c->span;
 	// Insert zero if missing
 	if (tok_is(c, TOKEN_DOTDOT) || tok_is(c, TOKEN_COLON))
 	{
@@ -62,6 +63,12 @@ bool parse_range(ParseContext *c, Range *range)
 	}
 
 	// Otherwise we have [1..] or [3:]
+	if (range->is_len)
+	{
+		sema_error_at(extend_span_with_token(start, c->prev_span), "Length-ranges using ':' may not elide the length.");
+		return false;
+	}
+
 	range->end_from_end = false;
 	range->end = 0;
 	return true;
diff --git a/src/version.h b/src/version.h
index c699b3b8d..2252f8397 100644
--- a/src/version.h
+++ b/src/version.h
@@ -1 +1 @@
-#define COMPILER_VERSION "0.4.613"
\ No newline at end of file
+#define COMPILER_VERSION "0.4.614"
\ No newline at end of file
diff --git a/test/test_suite/slices/slice_len_error.c3 b/test/test_suite/slices/slice_len_error.c3
new file mode 100644
index 000000000..a40a88097
--- /dev/null
+++ b/test/test_suite/slices/slice_len_error.c3
@@ -0,0 +1,21 @@
+int[8][8] a;
+fn void main()
+{
+   a[2..3];
+    a[2:1];
+    a[..3];
+    a[2..];
+    a[..];
+    a[2:1];
+    a[:4];
+}
+
+fn void test1()
+{
+    a[:]; // #error: not elide
+}
+
+fn void test2()
+{
+    a[2:]; // #error: not elide
+}
\ No newline at end of file
diff --git a/test/unit/stdlib/core/bitorder.c3 b/test/unit/stdlib/core/bitorder.c3
index aaca67af2..0c3e64626 100644
--- a/test/unit/stdlib/core/bitorder.c3
+++ b/test/unit/stdlib/core/bitorder.c3
@@ -18,12 +18,12 @@ fn void! test_read()
     assert(bitorder::read(&bytes, ULongBE) == 0x0102030405060708);
     assert(bitorder::read(&bytes, ULongLE) == 0x0807060504030201);
 
-    assert(bitorder::read(bytes[:], UShortBE) == 0x0102);
-    assert(bitorder::read(bytes[:], UShortLE) == 0x0201);
-    assert(bitorder::read(bytes[:], UIntBE) == 0x01020304);
-    assert(bitorder::read(bytes[:], UIntLE) == 0x04030201);
-    assert(bitorder::read(bytes[:], ULongBE) == 0x0102030405060708);
-    assert(bitorder::read(bytes[:], ULongLE) == 0x0807060504030201);
+    assert(bitorder::read(bytes[..], UShortBE) == 0x0102);
+    assert(bitorder::read(bytes[..], UShortLE) == 0x0201);
+    assert(bitorder::read(bytes[..], UIntBE) == 0x01020304);
+    assert(bitorder::read(bytes[..], UIntLE) == 0x04030201);
+    assert(bitorder::read(bytes[..], ULongBE) == 0x0102030405060708);
+    assert(bitorder::read(bytes[..], ULongLE) == 0x0807060504030201);
 }
 
 fn void! test_write()
@@ -36,10 +36,10 @@ fn void! test_write()
     assert(bitorder::read(buf, UShortBE) == x1);
 
     uint x2 = bitorder::read(bytes, UIntBE);
-    bitorder::write(x2, buf[:], UIntBE);
+    bitorder::write(x2, buf[..], UIntBE);
     assert(bitorder::read(buf, UIntBE) == x2);
 
     ulong x3 = bitorder::read(bytes, ULongBE);
-    bitorder::write(x3, buf[:], ULongBE);
+    bitorder::write(x3, buf[..], ULongBE);
     assert(bitorder::read(buf, ULongBE) == x3);
 }
\ No newline at end of file