diff --git a/Project.toml b/Project.toml
index 3251939c3..6b8abb913 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,6 +1,6 @@
 name = "DynamicPPL"
 uuid = "366bfd00-2699-11ea-058f-f148b4cae6d8"
-version = "0.23.6"
+version = "0.23.7"
 
 [deps]
 AbstractMCMC = "80f14c24-f653-4e6a-9b94-39d6b0f70001"
@@ -22,7 +22,7 @@ ZygoteRules = "700de1a5-db45-46bc-99cf-38207098b444"
 
 [compat]
 AbstractMCMC = "2, 3.0, 4"
-AbstractPPL = "0.5.3"
+AbstractPPL = "0.6"
 BangBang = "0.3"
 Bijectors = "0.13"
 ChainRulesCore = "0.9.7, 0.10, 1"
diff --git a/src/compiler.jl b/src/compiler.jl
index ffdcd4755..96e98938b 100644
--- a/src/compiler.jl
+++ b/src/compiler.jl
@@ -1,5 +1,34 @@
 const INTERNALNAMES = (:__model__, :__context__, :__varinfo__)
 
+"""
+    need_concretize(expr)
+
+Return `true` if `expr` needs to be concretized, i.e., if it contains a colon `:` or 
+requires a dynamic lens.
+
+# Examples
+
+```jldoctest; setup=:(using Setfield)
+julia> DynamicPPL.need_concretize(:(x[1, :]))
+true
+
+julia> DynamicPPL.need_concretize(:(x[1, end]))
+true
+
+julia> DynamicPPL.need_concretize(:(x[1, 1]))
+false
+"""
+function need_concretize(expr)
+    return Setfield.need_dynamic_lens(expr) || begin
+        flag = false
+        MacroTools.postwalk(expr) do ex
+            # Concretise colon by default
+            ex == :(:) && (flag = true) && return ex
+        end
+        flag
+    end
+end
+
 """
     isassumption(expr[, vn])
 
@@ -16,10 +45,13 @@ When `expr` is not an expression or symbol (i.e., a literal), this expands to `f
 
 If `vn` is specified, it will be assumed to refer to a expression which
 evaluates to a `VarName`, and this will be used in the subsequent checks.
-If `vn` is not specified, `AbstractPPL.drop_escape(varname(expr))` will be
+If `vn` is not specified, `AbstractPPL.varname(expr, need_concretize(expr))` will be
 used in its place.
 """
-function isassumption(expr::Union{Expr,Symbol}, vn=AbstractPPL.drop_escape(varname(expr)))
+function isassumption(
+    expr::Union{Expr,Symbol},
+    vn=AbstractPPL.drop_escape(varname(expr, need_concretize(expr))),
+)
     return quote
         if $(DynamicPPL.contextual_isassumption)(__context__, $vn)
             # Considered an assumption by `__context__` which means either:
@@ -194,7 +226,7 @@ function unwrap_right_left_vns(
     # for `i = size(left, 2)`. Hence the symbol should be `x[:, i]`,
     # and we therefore add the `Colon()` below.
     vns = map(axes(left, 2)) do i
-        return vn ∘ Setfield.IndexLens((Colon(), i))
+        return AbstractPPL.concretize(vn ∘ Setfield.IndexLens((Colon(), i)), left)
     end
     return unwrap_right_left_vns(right, left, vns)
 end
@@ -372,7 +404,7 @@ function generate_tilde(left, right)
     return quote
         $dist = $right
         $vn = $(DynamicPPL.resolve_varnames)(
-            $(AbstractPPL.drop_escape(varname(left))), $dist
+            $(AbstractPPL.drop_escape(varname(left, need_concretize(left)))), $dist
         )
         $isassumption = $(DynamicPPL.isassumption(left, vn))
         if $(DynamicPPL.isfixed(left, vn))
@@ -433,7 +465,7 @@ function generate_dot_tilde(left, right)
     @gensym vn isassumption value
     return quote
         $vn = $(DynamicPPL.resolve_varnames)(
-            $(AbstractPPL.drop_escape(varname(left))), $right
+            $(AbstractPPL.drop_escape(varname(left, need_concretize(left)))), $right
         )
         $isassumption = $(DynamicPPL.isassumption(left, vn))
         if $(DynamicPPL.isfixed(left, vn))
diff --git a/src/test_utils.jl b/src/test_utils.jl
index 394341c04..17898b9fe 100644
--- a/src/test_utils.jl
+++ b/src/test_utils.jl
@@ -543,7 +543,8 @@ function logprior_true_with_logabsdet_jacobian(
     return _demo_logprior_true_with_logabsdet_jacobian(model, s, m)
 end
 function varnames(model::Model{typeof(demo_dot_assume_matrix_dot_observe_matrix)})
-    return [@varname(s[:, 1]), @varname(s[:, 2]), @varname(m)]
+    s = zeros(1, 2) # used for varname concretization only
+    return [@varname(s[:, 1], true), @varname(s[:, 2], true), @varname(m)]
 end
 
 @model function demo_assume_matrix_dot_observe_matrix(
diff --git a/src/utils.jl b/src/utils.jl
index abd7b9da0..5c129f4a4 100644
--- a/src/utils.jl
+++ b/src/utils.jl
@@ -500,6 +500,12 @@ function BangBang.possible(
     return BangBang.implements(setindex!, C) &&
            promote_type(eltype(C), eltype(T)) <: eltype(C)
 end
+function BangBang.possible(
+    ::typeof(BangBang._setindex!), ::C, ::T, ::AbstractPPL.ConcretizedSlice, ::Integer
+) where {C<:AbstractMatrix,T<:AbstractVector}
+    return BangBang.implements(setindex!, C) &&
+           promote_type(eltype(C), eltype(T)) <: eltype(C)
+end
 
 # HACK(torfjelde): This makes it so it works on iterators, etc. by default.
 # TODO(torfjelde): Do better.
diff --git a/test/Project.toml b/test/Project.toml
index 1f3e6e4fe..b36a7e23a 100644
--- a/test/Project.toml
+++ b/test/Project.toml
@@ -22,7 +22,7 @@ Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"
 
 [compat]
 AbstractMCMC = "2.1, 3.0, 4"
-AbstractPPL = "0.5"
+AbstractPPL = "0.6"
 Bijectors = "0.13"
 Distributions = "0.25"
 DistributionsAD = "0.6.3"
diff --git a/test/varinfo.jl b/test/varinfo.jl
index de86a9e05..35ab30dcd 100644
--- a/test/varinfo.jl
+++ b/test/varinfo.jl
@@ -55,7 +55,7 @@
         @test inspace(@varname(z[1][:]), space)
         @test inspace(@varname(z[1][2:3:10]), space)
         @test inspace(@varname(M[[2, 3], 1]), space)
-        @test inspace(@varname(M[:, 1:4]), space)
+        @test_throws ErrorException inspace(@varname(M[:, 1:4]), space)
         @test inspace(@varname(M[1, [2, 4, 6]]), space)
         @test !inspace(@varname(z[2]), space)
         @test !inspace(@varname(z), space)