diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 2744a0e97..57e064de7 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -216,7 +216,7 @@ jobs:
       fail-fast: false
       matrix:
         build_type: [Release, Debug]
-        llvm_version: [17, 18, 19, 20]
+        llvm_version: [17, 18, 19]
 
     steps:
       - uses: actions/checkout@v4
@@ -496,7 +496,7 @@ jobs:
       matrix:
         ubuntu_version: [20.04, 22.04]
         build_type: [Release, Debug]
-        llvm_version: [17, 18, 19, 20]
+        llvm_version: [17, 18, 19]
 
     steps:
       - uses: actions/checkout@v4
diff --git a/releasenotes.md b/releasenotes.md
index 7690e3ed4..7fc411ddd 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -10,6 +10,7 @@
 - Generic methods were incorrectly registered as functions, leading to naming collisions. #1402
 - Deprecated inline generic types.
 - Deprecated tuple / triple types.
+- Converting a slice to a vector/array would copy too little data.
 
 ### Stdlib changes
 *None yet*
diff --git a/src/compiler/llvm_codegen_expr.c b/src/compiler/llvm_codegen_expr.c
index c8ee6bd6c..cf3199e99 100644
--- a/src/compiler/llvm_codegen_expr.c
+++ b/src/compiler/llvm_codegen_expr.c
@@ -1277,9 +1277,7 @@ void llvm_emit_slice_to_vec_array_cast(GenContext *c, BEValue *value, Type *to_t
 	LLVMTypeRef type = llvm_get_type(c, to_type);
 	AlignSize alignment = llvm_abi_alignment(c, type);
 	LLVMValueRef temp = llvm_emit_alloca(c, type, alignment, ".temp");
-	unsigned elements = LLVMGetTypeKind(type) == LLVMVectorTypeKind
-			? LLVMGetVectorSize(type) : LLVMGetArrayLength(type);
-	llvm_emit_memcpy(c, temp, alignment, pointer.value, element_alignment, elements);
+	llvm_emit_memcpy(c, temp, alignment, pointer.value, element_alignment, llvm_abi_size(c, type));
 	llvm_value_set_address(value, temp, to_type, alignment);
 }
 
diff --git a/test/unit/regression/vector_conversion.c3 b/test/unit/regression/vector_conversion.c3
index 1e8dce393..106e0aec4 100644
--- a/test/unit/regression/vector_conversion.c3
+++ b/test/unit/regression/vector_conversion.c3
@@ -16,6 +16,13 @@ fn void vector_array_inferred()
 	assert(w == int[<2>] { 4, 7 });
 }
 
+fn void vector_convert_slice()
+{
+	int[<2>] x = { 1, 2 };
+	int[2] y = { 4, 4 };
+	x *= y[:2];
+	assert(x == { 4, 8 });
+}
 fn void vector_convert_bool()
 {
 	bool[<2>] a = { true, false };