diff --git a/src/analysis/normed_space/star/basic.lean b/src/analysis/normed_space/star/basic.lean
index fcff072e8b481..84eaf1fd7220c 100644
--- a/src/analysis/normed_space/star/basic.lean
+++ b/src/analysis/normed_space/star/basic.lean
@@ -36,7 +36,7 @@ local postfix `⋆`:std.prec.max_plus := star
 
 /-- A normed star group is a normed group with a compatible `star` which is isometric. -/
 class normed_star_group (E : Type*) [semi_normed_group E] [star_add_monoid E] : Prop :=
-(norm_star : ∀ {x : E}, ∥x⋆∥ = ∥x∥)
+(norm_star : ∀ x : E, ∥x⋆∥ = ∥x∥)
 
 export normed_star_group (norm_star)
 attribute [simp] norm_star
@@ -46,16 +46,16 @@ variables {𝕜 E α : Type*}
 section normed_star_group
 variables [semi_normed_group E] [star_add_monoid E] [normed_star_group E]
 
-@[simp] lemma nnnorm_star (x : E) : ∥star x∥₊ = ∥x∥₊ := subtype.ext norm_star
+@[simp] lemma nnnorm_star (x : E) : ∥star x∥₊ = ∥x∥₊ := subtype.ext $ norm_star _
 
 /-- The `star` map in a normed star group is a normed group homomorphism. -/
 def star_normed_group_hom : normed_group_hom E E :=
-{ bound' := ⟨1, λ v, le_trans (norm_star.le) (one_mul _).symm.le⟩,
+{ bound' := ⟨1, λ v, le_trans (norm_star _).le (one_mul _).symm.le⟩,
   .. star_add_equiv }
 
 /-- The `star` map in a normed star group is an isometry -/
 lemma star_isometry : isometry (star : E → E) :=
-star_add_equiv.to_add_monoid_hom.isometry_of_norm (λ _, norm_star)
+star_add_equiv.to_add_monoid_hom.isometry_of_norm norm_star
 
 lemma continuous_star : continuous (star : E → E) := star_isometry.continuous
 
@@ -92,7 +92,7 @@ end normed_star_group
 
 instance ring_hom_isometric.star_ring_end [normed_comm_ring E] [star_ring E]
   [normed_star_group E] : ring_hom_isometric (star_ring_end E) :=
-⟨λ _, norm_star⟩
+⟨norm_star⟩
 
 /-- A C*-ring is a normed star ring that satifies the stronger condition `∥x⋆ * x∥ = ∥x∥^2`
 for every `x`. -/
@@ -179,7 +179,7 @@ norm_coe_unitary_mul ⟨U, hU⟩ A
 calc _ = ∥((U : E)⋆ * A⋆)⋆∥ : by simp only [star_star, star_mul]
   ...  = ∥(U : E)⋆ * A⋆∥    : by rw [norm_star]
   ...  = ∥A⋆∥               : norm_mem_unitary_mul (star A) (unitary.star_mem U.prop)
-  ...  = ∥A∥                : norm_star
+  ...  = ∥A∥                : norm_star _
 
 lemma norm_mul_mem_unitary (A : E) {U : E} (hU : U ∈ unitary E) : ∥A * U∥ = ∥A∥ :=
 norm_mul_coe_unitary A ⟨U, hU⟩
@@ -210,7 +210,7 @@ variables (𝕜)
 /-- `star` bundled as a linear isometric equivalence -/
 def starₗᵢ : E ≃ₗᵢ⋆[𝕜] E :=
 { map_smul' := star_smul,
-  norm_map' := λ x, norm_star,
+  norm_map' := norm_star,
   .. star_add_equiv }
 
 variables {𝕜}
diff --git a/src/analysis/normed_space/star/matrix.lean b/src/analysis/normed_space/star/matrix.lean
index f045ac73ff595..5044a55c132d0 100644
--- a/src/analysis/normed_space/star/matrix.lean
+++ b/src/analysis/normed_space/star/matrix.lean
@@ -28,7 +28,7 @@ begin
   refine le_antisymm (by simp [matrix.norm_le_iff, M.norm_entry_le_entrywise_sup_norm]) _,
   refine ((matrix.norm_le_iff (norm_nonneg _)).mpr (λ i j, _)).trans
     (congr_arg _ M.star_eq_conj_transpose).ge,
-  exact (normed_star_group.norm_star).symm.le.trans Mᴴ.norm_entry_le_entrywise_sup_norm
+  exact (norm_star _).ge.trans Mᴴ.norm_entry_le_entrywise_sup_norm
 end
 
 @[priority 100] -- see Note [lower instance priority]
diff --git a/src/topology/continuous_function/bounded.lean b/src/topology/continuous_function/bounded.lean
index f83d3f09fb856..13c2843ff26b2 100644
--- a/src/topology/continuous_function/bounded.lean
+++ b/src/topology/continuous_function/bounded.lean
@@ -1202,8 +1202,7 @@ instance `pi.has_star`. Upon inspecting the goal, one sees `⊢ ⇑(star f) = st
 @[simp] lemma star_apply (f : α →ᵇ β) (x : α) : star f x = star (f x) := rfl
 
 instance : normed_star_group (α →ᵇ β) :=
-{ norm_star := λ f, by
-  { simp only [norm_eq], congr, ext, conv_lhs { find (∥_∥) { erw (@norm_star β _ _ _ (f x)) } } } }
+{ norm_star := λ f, by simp only [norm_eq, star_apply, norm_star] }
 
 instance : star_module 𝕜 (α →ᵇ β) :=
 { star_smul := λ k f, ext $ λ x, star_smul k (f x) }
diff --git a/src/topology/continuous_function/zero_at_infty.lean b/src/topology/continuous_function/zero_at_infty.lean
index 24a7064d6e6dd..f747021fa0f6d 100644
--- a/src/topology/continuous_function/zero_at_infty.lean
+++ b/src/topology/continuous_function/zero_at_infty.lean
@@ -438,7 +438,7 @@ instance : star_add_monoid C₀(α, β) :=
   star_add := λ f g, ext $ λ x, star_add (f x) (g x) }
 
 instance : normed_star_group C₀(α, β) :=
-{ norm_star := λ f, @norm_star _ _ _ _ f.to_bcf }
+{ norm_star := λ f, (norm_star f.to_bcf : _) }
 
 end star